Fixing method of in-wheel motor and in-wheel motor system

ABSTRACT

A non-rotary case to which the motor stator of an inwheel motor is fixed is connected to a knuckle which is a part around the wheel of a vehicle by a first elastic member, a rotary case to which the rotor of the motor is fixed and rotatably connected to the non-rotary case through a bearing is connected to the wheel by a second elastic member so as to float-mount the inwheel motor to parts around the wheel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inwheel motor system for use in avehicle having direct drive wheels as drive wheels and to an inwheelmotor mounting method.

2. Description of the Prior Art

Nowadays, an inwheel motor system that a motor is incorporated in eachwheel is been adopted in vehicles which are driven by a motor, such aselectric cars, to achieve a high space efficiency and high transmissionefficiency of driving force.

FIG. 78 shows that a direct drive motor of a hollow outer rotor type(inwheel motor) 70 disclosed by JP 2676025 is mounted. In this inwheelmotor 70, a stator 70S is connected to and supported by an upright 71which is a fixed portion, located on the inner side of the wheel disk 73of a direct drive wheel 72, and also connected to a rotary shaft 74coupled to the above wheel disk 73 through a bearing 74J. A rotor 70Raround the above stator 70S is supported by a first bracket 75 aconnected to the above rotary shaft 74 and a second bracket 75 b whichis rotatably fixed to the upright 71 through a bearing 71J. Since therotor 70R is thereby rotatably connected to the stator 70S, torque canbe transmitted to the wheel 72 by driving the inwheel motor 70 so thatthe wheel 72 can be directly driven.

There are proposed some methods of mounting an inwheel motor: one shownin FIG. 79 in which a rotor 80R having magnetic means (permanent magnet)80M is installed in a housing 82 fixed to a wheel 81, a stator 80Shaving a coil 80C is placed on the inner side of the above magneticmeans 80M and fixed to a hollow shaft 84 connected to a knuckle 83, andthe inner and outer side walls 82 a and 82 b of the above housing 82 areconnected to the above stator 80S through bearings 84 a and 84 b torotatably link the rotor 80R of an inwheel motor 80 to the stator 80S(for example, Japanese Patent Publication No. 9-506236), and one shownin FIG. 80 in which the stator 90S of an inwheel motor 90 is fixed to asteering knuckle 93 connected to a hub portion 92 through a bearing 91and in which the rim portion 94 a of a wheel 94 is used as the rotor ofthe motor to be rotatably linked to the stator 90S (for example,Japanese Laid-open Patent Application No. 10-305735).

In a vehicle having a suspension unit such as a spring around eachwheel, as the mass of an unsprung part such as a wheel, knuckle orsuspension arm, so-called “unsprung mass” increases, the contact forceof a tire fluctuates when the vehicle runs over a uneven road, resultingin deteriorated road holding properties.

Even when the mass of the body of a vehicle, so-called “sprung mass” issmall, the road holding properties also deteriorate. Therefore, toimprove the road holding properties, the unsprung mass must be made muchsmaller than the sprung mass.

However, since the motor stator of the inwheel motor is rotatably fixedto a spindle shaft connected to a part called “upright” or “knuckle”which is one of parts around the wheels of the vehicle, the unsprungmass increases when the above inwheel motor is mounted, therebydeteriorating the road holding properties.

Therefore, the inwheel motor vehicle is rarely used although it is avery attractive electric car having excellent space efficiency andtransmission efficiency of driving force.

SUMMARY OF THE INVENTION

It is an object of the present invention which has been made in view ofthe problems of the prior art to provide a method of mounting an inwheelmotor and an inwheel motor system both of which are capable of reducingthe tire contact force fluctuation of a vehicle to improve the roadholding properties of the vehicle.

According to a first aspect of the present invention, there is provideda method of mounting an inwheel motor to a direct drive wheel,comprising mounting the motor to an unsprung mass corresponding portionof a vehicle by a buffer member or a buffer unit.

The “unsprung mass corresponding portion” as used herein denotes a wheelor a part around the wheel such as a knuckle or suspension arm.

According to a second aspect of the present invention, there is provideda method of mounting an inwheel motor, wherein the non-rotary case ofthe motor and a knuckle are interconnected by a first elastic member,and the rotary case of the motor and the wheel are interconnected by asecond elastic member.

According to a third aspect of the present invention, there is provideda method of mounting an inwheel motor, wherein the non-rotary case ofthe motor for supporting the stator of the motor and a knuckle which isa part around the wheel of the vehicle are interconnected by adirect-acting guide unit, and the rotary case of the motor forsupporting the rotor of the motor and the wheel are interconnected by adriving force transmission unit which can be eccentric from the wheel inthe radial direction.

According to a fourth aspect of the present invention, there is provideda method of mounting an inwheel motor, wherein the non-rotary case ofthe motor and a knuckle are interconnected by a direct-acting guide unitincluding a damper, and the rotary case of the motor and the wheel areinterconnected by a second elastic member.

According to a fifth aspect of the present invention, there is provideda method of mounting an inwheel motor to a direct drive wheel,comprising mounting the non-rotary case of the motor on a car body sideby a buffer unit.

According to a sixth aspect of the present invention, there is provideda method of mounting an inwheel motor, wherein the motor is mounted toensure that the resonance frequency of the mounted motor should becomehigher than the resonance frequency of sprung mass and lower than theresonance frequency of unsprung mass.

According to a seventh aspect of the present invention, there isprovided an inwheel motor system comprising a hollow electric motor in awheel portion to drive the wheel, wherein the motor is mounted to anunsprung mass corresponding portion of a wheel, a car body side, or bothof them, by a buffer member or a buffer unit.

According to an eighth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor and the wheel areinterconnected by a constant-velocity universal joint or by a drivingforce transmission unit which can be eccentric from the wheel in theradial direction.

According to a ninth aspect of the present invention, there is providedan inwheel motor system, wherein the driving force transmission unit isa coupling unit which comprises a plurality of hollow disk-like platesand direct-acting guides for interconnecting adjacent plates and forguiding the adjacent plates in the radial direction of the disk.

According to a tenth aspect of the present invention, there is providedan inwheel motor system, wherein the non-rotary case of the motor forsupporting the stator of the motor and a knuckle which is a part aroundthe wheel of a vehicle are interconnected by a direct-acting guide unit.

According to an eleventh aspect of the present invention, there isprovided an inwheel motor system, wherein a buffer member or a bufferunit is provided between the non-rotary case of the motor and theknuckle or/and between the rotary case and the wheel.

According to a twelfth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of the motor and a knuckle which is apart around the wheel of the vehicle are interconnected by a firstelastic member, and the rotary case of the motor for supporting a rotorand the wheel are interconnected by a second elastic member.

According to a thirteenth aspect of the present invention, there isprovided an inwheel motor system, wherein at least one or both of thefirst and second elastic members are an air spring. According to afourteenth aspect of the present invention, there is provided an inwheelmotor system, wherein the second elastic member is cylindrical, one endof this cylinder is connected to the wheel, and the other end isconnected to the rotary case.

According to a fifteenth aspect of the present invention, there isprovided an inwheel motor system, wherein the wheel and the rotary caseare interconnected by 16 or less board-like elastic members disposed atequal intervals in parallel to the tangent direction of the wheel.

According to a sixteenth aspect of the present invention, there isprovided an inwheel motor system, wherein rotary joint units whose axesare in the tangent direction of the motor are provided on both end facesin the width direction of the plate-like elastic members.

According to a seventeenth aspect of the present invention, there isprovided an inwheel motor system, wherein ribs extending from the rotarycase toward the wheel and ribs extending from the wheel toward therotary case are interconnected by an elastic member at a plurality ofsites.

According to an eighteenth aspect of the present invention, there isprovided an inwheel motor system, wherein the vertical elasticcoefficient of a material constituting the first and second elasticmembers is 1 to 120 MPa.

According to a nineteenth aspect of the present invention, there isprovided an inwheel motor system, wherein the vertical elasticcoefficient of a material constituting the first and second elasticmembers is 10 to 300 GPa.

According to a twentieth aspect of the present invention, there isprovided an inwheel motor system, wherein the first elastic member has alower elastic modulus in the vertical direction of the vehicle than anelastic modulus in the longitudinal direction.

According to a twenty-first aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case isconnected to the knuckle by a direct-acting guide unit having a springand a damper in place of the first elastic member.

According to a twenty-second aspect of the present invention, there isprovided an inwheel motor system, wherein the rotary case is connectedto the wheel by a constant-velocity universal joint.

According to a twenty-third aspect of the present invention, there isprovided an inwheel motor system, wherein the second elastic member ismounted at the center position of the mass of the motor in the widthdirection of the motor.

According to a twenty-fourth aspect of the present invention, there isprovided an inwheel motor system, wherein the rotary case is connectedto the wheel by a coupling unit comprising a plurality of hollowdisk-like plates and direct-acting guides for interconnecting adjacentplates and for guiding the adjacent plates in the radial direction ofthe disk.

According to a twenty-fifth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of the motor is connected to the knucklewhich is a part around the wheel of the vehicle by a buffer member orbuffer unit, and the rotary case of the motor is connected to the wheelby a coupling unit comprising a plurality of hollow disk-like plates anddirect-acting guides for interconnecting adjacent plates and for guidingthe adjacent plates in the radial direction of the disk.

According to a twenty-sixth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of the motor is connected to the knucklewhich is a part around the wheel of the vehicle by a buffer member orbuffer unit, and the rotary case of the motor is connected to the wheelby a hollow disk-like plate having a plurality of direct-acting guideson the motor side and the wheel side.

According to a twenty-seventh aspect of the present invention, there isprovided an inwheel motor system, wherein the direct-acting guides aredisposed at the same positions on the front and back sides of the hollowdisk-like plate at an interval of 90° or 180° in the circumferentialdirection of the plate.

According to a twenty-eighth aspect of the present invention, there isprovided an inwheel motor system, wherein the working directions of allthe direct-acting guides on the motor side are 45° from the radialdirection of the hollow disk-like plate, and the working directions ofall the direct-acting guides on the wheel side are perpendicular to theworking directions of all the direct-acting guides on the motor side.

According to a twenty-ninth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of the motor is connected to the knucklewhich is a part around the wheel of the motor by a buffer member or abuffer unit, and the rotary case of the motor is connected to the wheelby a first hollow disk-like plate comprising a plurality ofdirect-acting guides on the motor side and the wheel side and by asecond hollow disk-like plate disposed on the inner side of the firsthollow disk-like plate and comprising a plurality of direct-actingguides arranged in an opposite way to that of the first hollow disk-likeplate.

According to a thirtieth aspect of the present invention, there isprovided an inwheel motor system, wherein the direct-acting guides aredisposed at the same positions on the front and back sides of the firstand second hollow disk-like plates at an interval of 90° or 180° in thecircumferential direction of the first and second hollow disk-likeplates, the working directions of all the direct-acting guides on themotor side of the first and second hollow disk-like plates are 45° fromthe radial direction of the plates, and the working directions of allthe direct-acting guides on the wheel side of the plates areperpendicular to the working directions of the direct-acting guides onthe motor side.

According to a thirty-first aspect of the present invention, there isprovided an inwheel motor system, wherein the mass of the first hollowdisk-like plate is made equal to the mass of the second hollow disk-likeplate.

According to a thirty-second aspect of the present invention, there isprovided an inwheel motor system, wherein each of the direct-actingguides consists of a guide rail having at least one recess or projectionextending in the radial direction of the plate and of a guide member tobe engaged with the guide rail.

According to a thirty-third aspect of the present invention, there isprovided an inwheel motor system, wherein steel balls are placed betweenthe guide rail and the guide member.

According to a thirty-fourth aspect of the present invention, there isprovided an inwheel motor system, wherein grooves extending in theradial direction are formed in the opposing sides of the plates, andsteel balls which can move along the grooves are placed between theplates to guide the adjacent plates in the radial direction of the disk.

According to a thirty-fifth aspect of the present invention, there isprovided an inwheel motor system, wherein when the number of the platesis represented by N, the plates are disposed in such a manner that theangle formed by adjacent direct-acting guides or grooves in the axialdirection of the plates is incremented by 180/(N−1)° from the endportion.

According to a thirty-sixth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of the motor and a knuckle which is apart around the wheel of the vehicle are interconnected by a buffermember comprising at least one pair of substantially A-shaped orH-shaped link units, each having two arms rotatably interconnected by aspring and a damper, the end of one arm being connected to thenon-rotary case and the end of the other arm being connected to theknuckle.

According to a thirty-seventh aspect of the present invention, there isprovided an inwheel motor system, wherein a shaft type suspension unitis provided, and the non-rotary case of the motor for supporting thestator of the motor and the shaft are interconnected by a buffer membercomprising at least one pair of substantially A-shaped or H-shaped linkunits, each having two arms rotatably interconnected by a spring and adamper, the end of one arm being connected to the non-rotary case andthe end of the other arm being connected to the shaft.

According to a thirty-eighth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor and a knuckle are interconnected by two plates whose workingdirections are limited to the vertical direction of the vehicle bydirect-acting guides, and the two plates are interconnected by springsand dampers which operate in the vertical direction of the vehicle.

According to a thirty-ninth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor is supported to aknuckle which is a part around the wheel by direct-acting guides and abuffer unit in such a manner that it can move in the vertical directionof the vehicle, and the buffer unit has valves between a hydrauliccylinder and a reservoir tank.

According to a fortieth aspect of the present invention, there isprovided an inwheel motor system, wherein the piston upper chamber andpiston lower chamber of the hydraulic cylinder are each provided with aworking oil passage having an independent valve and a reservoir tank.

According to a forty-first aspect of the present invention, there isprovided an inwheel motor system, wherein the piston upper chamber andpiston lower chamber of the hydraulic cylinder are each provided with aworking oil passage having an independent valve, and the two working oilpassages are connected to a common reservoir tank.

According to a forty-second aspect of the present invention, there isprovided an inwheel motor system, wherein the piston upper chamber andpiston lower chamber of the hydraulic cylinder are interconnected byworking oil passages, each having an independent valve, and the pistonlower chamber is connected to a reservoir tank.

According to a forty-third aspect of the present invention, there isprovided an inwheel motor system, wherein the hub portion of the systemhas a connection unit with the output shaft of the power engine of thevehicle.

According to a forty-fourth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor is an outer rotortype motor.

According to a forty-fifth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor is an inner rotortype motor.

According to a forty-sixth aspect of the present invention, there isprovided an inwheel motor system having an electric motor in a wheelportion to drive a wheel, wherein

the motor is a geared motor comprising a hollow inner rotor type motorand a speed reducing gear, the non-rotary case of this geared motor anda knuckle which is a part around the wheel of a vehicle areinterconnected by a buffer member, and the output shaft of the speedreducer and the wheel are linked by a shaft having a universal joint.

According to a forty-seventh aspect of the present invention, there isprovided an inwheel motor system, wherein a direct-acting guide forguiding the motor in a vertical direction is interposed between thenon-rotary case and the knuckle.

According to a forty-eighth aspect of the present invention, there isprovided an inwheel motor system, wherein the non-rotary case of themotor for supporting the stator of a hollow outer rotor type motor isconnected to a knuckle which is a part around the wheel of a vehicle,the rotary case of the motor for supporting the rotor of the motor isconnected to the wheel, and a wheel support unit is provided on theinner side of the motor.

According to a forty-ninth aspect of the present invention, there isprovided an inwheel motor system, wherein the rotary case is inscribedin the wheel, and the knuckle and the hub portion of the systemconnected to the rotation axis of the wheel are interconnected by a hubbearing provided on the inner side of the hollow motor to support thewheel.

According to a fiftieth aspect of the present invention, there isprovided an inwheel motor system, wherein the rotary case is connectedto the wheel by elastic members.

According to a fifty-first aspect of the present invention, there isprovided an inwheel motor system, wherein the vertical elasticcoefficient of the material of the elastic members is 1 to 120 MPa.

According to a fifty-second aspect of the present invention, there isprovided an inwheel motor system, wherein a brake disk or brake drum ismounted to the hub portion.

According to a fifty-third aspect of the present invention, there isprovided an inwheel motor system, wherein the hub portion of the systemhas a connection unit with the output shaft of the power engine of thevehicle.

According to a fifty-fourth aspect of the present invention, there isprovided an inwheel motor system having a hollow electric motor in awheel portion to drive a wheel, wherein

the motor is supported to a knuckle which is a part around the wheel ofa vehicle by direct-acting guides and buffer members in the verticaldirection of the vehicle and by direct-acting guides and buffer membersin the longitudinal direction of the vehicle, and the rotary case of themotor and the wheel are interconnected by a flexible coupling orconstant-velocity universal joint in such a manner that they can beeccentric from each other.

According to a fifty-fifth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor is an outer rotortype motor.

According to a fifty-sixth aspect of the present invention, there isprovided an inwheel motor system, wherein the motor is an inner rotortype motor.

According to a fifty-seventh aspect of the present invention, there isprovided an inwheel motor system having an electric motor in a wheelportion to drive a wheel, wherein

the motor is a geared motor comprising a hollow inner rotor type motorand a speed reducing gear, the non-rotary case of this geared motor issupported to a knuckle which is a part around the wheel by direct-actingguides and buffer members in the vertical direction and by direct-actingguides and buffer members in the longitudinal direction of the vehicle,and the output shaft of the speed reducer and the wheel areinterconnected by a shaft having a universal joint.

According to a fifty-eight aspect of the present invention, there isprovided an inwheel motor system having a hollow electric motor in awheel portion to drive a vehicle, comprising a first annular case insideof which is opened in respect to a radial direction of the same, asecond annular case arranged coaxially with the first annular case andplaced inner side of the first annular case and outside of which isopened outwardly with respect to a radial direction facing the innerside opened portion, either one of the cases constitutes a rotary caseprovided with a motor rotor, another case constitutes a non-rotary caseprovided with a motor stator, the non-rotary case and the rotary caseare rotatively coupled through a bearing, wherein the non-rotary case isconnected to a knuckle and the rotary case is connected to a wheel.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 1 of the present invention;

FIG. 2 is a front sectional view showing the constitution of the inwheelmotor system according to Embodiment 1 of the present invention;

FIG. 3 is a diagram showing the moving state of an inwheel motoraccording to Embodiment 1 of the present invention;

FIG. 4 is a diagram of another inwheel motor system according toEmbodiment 1 of the present invention;

FIG. 5 is a diagram of still another inwheel motor system according toEmbodiment 1 of the present invention;

FIG. 6 is a diagram showing the constitution of an inwheel motor systemcomprising an air spring according to the present invention;

FIG. 7 is a diagram showing the constitution of an inwheel motor systemcomprising a direct-acting guide unit including a damper according tothe present invention;

FIG. 8 is a diagram showing the moving state of the inwheel motor ofFIG. 7;

FIG. 9 is a diagram showing the constitution of an inwheel motor systemcomprising a damper unit for interconnecting ribs by an elastic memberaccording to the present invention;

FIG. 10 is a diagram showing the moving state of the inwheel motor whena cylindrical elastic member is used;

FIGS. 11( a) and 11(b) are diagrams showing a method of arrangingboard-like elastic members according to the present invention;

FIG. 12 is a graph showing the relationship between the number ofboard-like elastic members and vertical stiffness;

FIG. 13 is diagram showing the constitution of a hybrid type inwheelmotor system according to the present invention;

FIG. 14 is a diagram showing the constitution of an inwheel motor systemcomprising a constant-velocity universal joint according to Embodiment 2of the present invention;

FIG. 15 is a diagram for explaining the operation of theconstant-velocity universal joint;

FIG. 16 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 3 of the present invention;

FIG. 17 is a sectional view of the key section of the inwheel motorsystem according to Embodiment 3 of the present invention;

FIG. 18 is a diagram of the arrangement of direct-acting guides;

FIG. 19 is a diagram showing the constitution of the direct-actingguide;

FIG. 20 is a diagram of another flexible coupling;

FIG. 21 is a sectional view of the key section of FIG. 20;

FIG. 22 is a diagram for explaining the operation of the flexiblecoupling shown in FIG. 20 and FIG. 21;

FIG. 23 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 4 of the present invention;

FIG. 24 is a diagram showing the constitution of a flexible couplingaccording to Embodiment 4 of the present invention;

FIG. 25 is a diagram for explaining the operation of the flexiblecoupling according to Embodiment 4 of the present invention;

FIG. 26 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 5 of the present invention;

FIG. 27 is a diagram showing the constitution of a flexible couplingaccording to Embodiment 5 of the present invention;

FIGS. 28( a) to 28(c) are diagrams for explaining the operation of theflexible coupling according to Embodiment 5 of the present invention;

FIG. 29 is a diagram of another flexible coupling according to thepresent invention;

FIG. 30 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 6 of the present invention;

FIG. 31 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 7 of the present invention;

FIG. 32 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 8 of the present invention;

FIG. 33 is a diagram showing the constitution of a buffer unit accordingto Embodiment 8 of the present invention;

FIG. 34 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 9 of the present invention;

FIG. 35 is a diagram showing the constitution of a buffer unitcomprising a hydraulic cylinder according to Embodiment 9 of the presentinvention;

FIG. 36 is a diagram showing the details of the buffer unit comprising ahydraulic cylinder;

FIG. 37 is a diagram of another buffer unit comprising a hydrauliccylinder according to Embodiment 9 of the present invention;

FIG. 38 is a diagram of still another buffer unit comprising a hydrauliccylinder according to Embodiment 9 of the present invention;

FIG. 39 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 10 of the presentinvention;

FIG. 40 is a sectional view of the key section of the inwheel motorsystem according to Embodiment 10 of the present invention;

FIG. 41 is a diagram showing a car vibration model in the inwheel motorsystem of the prior art;

FIG. 42 is a diagram showing a car vibration model when a dynamic damperis mounted to the inwheel motor system of the prior art;

FIG. 43 is a diagram showing a car vibration model in the inwheel motorsystem of the present invention;

FIG. 44 is a table showing mass, spring constant and others in each carvibration model;

FIG. 45 is a graph showing the analytical results of car vibrationmodels;

FIG. 46 is a graph showing the relationship between tire contact loadand cornering power (CP);

FIG. 47 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 11 of the presentinvention;

FIG. 48 is a sectional view of the key section of another inwheel motorsystem according to the present invention;

FIG. 49 is a longitudinal sectional view showing the constitution ofanother inwheel motor system according to the present invention;

FIG. 50 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 12 of the presentinvention;

FIG. 51 is a longitudinal sectional view showing the constitution ofanother inwheel motor system according to the present invention;

FIG. 52 is a diagram showing a car vibration model in the inwheel motorsystem of the prior art;

FIG. 53 is a diagram showing a car vibration model in the inwheel motorsystem of FIG. 50 of the present invention;

FIG. 54 is a diagram showing a car vibration model in the inwheel motorsystem of FIG. 51 of the present invention;

FIG. 55 is a table showing mass, spring constant and others in each carvibration model;

FIG. 56 is a graph showing the analytical results of car vibrationmodels;

FIG. 57 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 13 of the presentinvention;

FIG. 58 is a sectional view of the key section of the inwheel motorsystem according to Embodiment 13 of the present invention;

FIG. 59 is a diagram showing the constitution and operation of elements44 in FIG. 58 according to Embodiment 13 of the present invention;

FIG. 60 is a diagram showing a car vibration model in the inwheel motorsystem of the prior art;

FIG. 61 is a diagram showing a car vibration model when a dynamic damperis mounted to the inwheel motor system of the prior art;

FIG. 62 is a diagram showing a car vibration model in the inwheel motorsystem of the present invention;

FIG. 63 is a table showing mass, spring constant and others in each carvibration model;

FIG. 64 is a graph showing the analytical results of car vibrationmodels;

FIG. 65 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 14 of the presentinvention;

FIG. 66 is a diagram showing how to mount the inwheel motor system ofEmbodiment 14

FIG. 67 is a longitudinal sectional view showing the constitution ofanother inwheel motor system according to the present invention;

FIG. 68 is a longitudinal sectional view showing the constitution of aninwheel motor system according to Embodiment 15 of the presentinvention;

FIG. 69 is a sectional view of the key section of FIG. 68;

FIG. 70 is a diagram showing how to mount the inwheel motor system ofEmbodiment 15;

FIGS. 71( a) and 71(b) are diagrams showing car vibration models in theelectric car system of the prior art;

FIGS. 72( a) and 72(b) are diagrams showing car vibration models in theinwheel motor system of the prior art;

FIGS. 73( a) and 73(b) are diagrams showing car vibration models inwhich a dynamic damper is added to the inwheel motor system of the priorart;

FIGS. 74( a) and 74(b) are diagrams showing car vibration models in theinwheel motor system of the present invention;

FIG. 75 is a table showing mass, spring constant and others in each carvibration model;

FIG. 76 is a graph showing the analytical results of car vibrationmodels;

FIG. 77 is a graph showing the analytical results of car vibrationmodels;

FIG. 78 is a diagram showing the constitution of the inwheel motorsystem of the prior art;

FIG. 79 is a diagram showing the constitution of the inwheel motorsystem of the prior art; and

FIG. 80 is a diagram showing the constitution of the inwheel motorsystem of the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described withreference to the accompanying drawings hereinunder.

Embodiment 1

FIG. 1 and FIG. 2 are diagrams showing the constitution of an inwheelmotor system according to Embodiment 1 of the present invention. FIG. 1is a longitudinal sectional view and FIG. 2 is a front sectional view ofthe inwheel motor system. In these figures, reference numeral 1 denotesa tire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b,and 3 denotes an inwheel motor of an outer rotor type comprising a motorstator (to be simply referred to as “stator” hereinafter) 3S fixed to anon-rotary case 3 a provided on the inner side in a radial direction anda motor rotor (to be simply referred to as “rotor” hereinafter) 3R fixedto a rotary case 3 b rotatably fixed to the above non-rotary case 3 athrough a bearing 3 j and provided on the outer side in the radialdirection. An air gap 3 g is formed between the above rotor 3R and theabove stator 3S. Reference numeral 4 represents a hub portion connectedto the rotation axis of the above wheel 2, 5 represents a knucklecoupled to upper and lower suspension arms 6 a and 6 b, 7 represents asuspension member which is a shock absorber or the like, and 8represents a brake which is a brake disk comprising a brake rotor 8 amounted to the hub portion 4 and a brake caliper 8 b. Another type ofbrake such as a brake drum may be used as the brake 8.

In this embodiment, the non-rotary case 3 a to which the stator 3S ofthe above inwheel motor 3 is fixed is connected to the knuckle 5 whichis a part around the wheel of the vehicle through a first elastic member11 which is made from an elastic material such as rubber and through aconnection member 12 having a support member 12 a for supporting theabove first elastic member 11 from the inner side in the radialdirection and a plurality of arm portions 12 b extending toward theknuckle 5 from the above support member 12 a, and the rotary case 3 b towhich the rotor 3R is fixed and which is rotatably connected to theabove non-rotary case 3 a through the bearing 3 j is connected to thewheel 2 through a second elastic member 13 in order to float-mount theinwheel motor 3 to a part around each wheel such as the knuckle 5.

Therefore, the rotation axis of the above inwheel motor 3 can move inthe radial direction independently of the rotation axis of the wheel 2.That is, since the inwheel motor 3 is rotatably divided into an outersection and an inner section in the radical direction with the bearing 3j as the boundary therebetween as shown in FIG. 3, the above rotary case3 b to which the rotor 3R is fixed rotates and transmits its torque tothe wheel 2 to which the tire 1 is mounted while the rotation axis ofthe above inwheel motor 3 moves in the radial direction independently ofthe shaft.

In the above constitution, the mass of the inwheel motor 3 is separatedfrom an unsprung mass corresponding portion of the vehicle, such as thewheel 2 or the knuckle 5, and functions as the mass of a so-calleddynamic damper. Therefore, the above dynamic damper serves to reduce atire contact force fluctuation (to be abbreviated as TCFF hereinafter)when the vehicle runs over an uneven road, thereby improving the roadholding properties of the vehicle. Even when the vehicle runs over a badroad, as vibration is not directly transmitted to the above inwheelmotor 3, a load on the inwheel motor 3 imposed by vibration is reduced.

At this point, the above motor 3 is mounted by suitably selecting themass of the above motor 3 and the elastic constants of the first andsecond elastic members 11 and 13 which are buffer members to ensure thatthe resonance frequency of a motor section including the above mountedinwheel motor 3 should become higher than the resonance frequency of thesprung mass (car body) of the vehicle and lower than the resonancefrequency of the unsprung mass including the wheel 2 and the knuckle 5,thereby making it possible to effectively reduce the level of TCFF whenthe vehicle runs over an uneven road.

Since the mass of the vehicle to be applied to each wheel is supportedby the above hub portion 4 due to the adoption of this constitution, aload on the inwheel motor 3 becomes small with the result that a changein the air gap 3 g formed between the stator 3S and the rotor 3R isreduced. Therefore, as the stiffness of the above non-rotary case 3 aand the stiffness of the rotary case 3 b can be reduced, the mass of theinwheel motor 3 can be reduced.

The spring constant in the radial direction of the above first elasticmember 11 is set to a lower level in the vertical direction of thevehicle than that in the longitudinal direction, whereby the inwheelmotor 3 can be moved only in substantially the vertical direction,thereby making it possible to suppress the co-rotation of the wheel 2and the inwheel motor 3 and to improve the rotation drive efficiency ofthe wheel.

In order to adjust the spring constant of the above first elastic member11 to a low level in the vertical direction of the vehicle and to a highlevel in the longitudinal direction, elastic members 11 a and 11 b areprovided only in the longitudinal direction as shown in FIG. 4, or anoval elastic member 11 c having a long axis in the longitudinaldirection is used as the first elastic members 11 as shown in FIG. 5.When the above oval elastic member 11 c is used, as shown in FIG. 5, theknuckle 5 must conform to the shape of the above elastic member 11 c.

In order to adjust stiffness to a low level in the vertical directionand to a high level in the rotation direction, it is important tobalance material stiffness with shape stiffness. When the first elasticmember 11 and the second elastic member 13 are made from an elasticmaterial such as rubber as in this embodiment, to obtain predeterminedstiffness, a material having a vertical elastic coefficient of 1 to 120MPa is preferably used as the material of the above first and secondelastic members 11 and 13. The above elastic coefficient is morepreferably 1 to 40 MPa.

When a spring member such as a metal spring is used as the first andsecond elastic members 11 and 13, the vertical elastic coefficient ofthe material of the above first and second elastic members 11 and 13 ispreferably set to 10 to 300 GPa.

In this Embodiment 1, the non-rotary case 3 a to which the stator 3S ofthe inwheel motor 3 is fixed is connected to the knuckle 5 which is apart around the wheel of the vehicle through the first elastic member 11mounted to the connection member 12 extending from the knuckle 5, andthe rotary case 3 b to which the rotor 3R is fixed is connected to thewheel 2 through the second elastic member 13 so that the inwheel motor 3serves as the weight of a dynamic damper for the unsprung mass, therebymaking it possible to reduce the level of TCFF when the vehicle runsover an uneven road, to improve the road holding properties of thevehicle and to reduce a load on the inwheel motor 3 imposed byvibration.

By adopting the inwheel motor system of the present invention, aninwheel motor car which has excellent space efficiency, excellenttransmission efficiency of driving force and high road holdingproperties can be realized.

In the above Embodiment 1, the non-rotary case 3 a of the inwheel motor3 is mounted to the knuckle 5 through the first elastic member 11, andthe rotary case 3 b is mounted to the wheel 2 through the second elasticmember 13. When tire-like ring air springs 11T and 13T as shown in FIG.6 are used in place of the above first and second elastic members 11 and13, respectively, a spring constant in a shearing direction can be madehigh in spite of a low spring constant in the radial direction, therebymaking it possible to constitute lightweight and highly elastic members.

As shown in FIG. 7 and FIG. 8, the non-rotary case 3 a and the knuckle 5may be connected by a direct-acting guide unit 14 which comprises adamper 14 a and a support member 14 b for supporting the damper 14 a inthe vertical direction of the vehicle in place of the above firstelastic member 11 and the above connection member 12. Thereby, theinwheel motor 3 can be confined to vertical movement while generatingattenuation force with the result that the co-rotation of the wheel 2and the inwheel motor 3 can be suppressed and rotation drive efficiencycan be improved.

As shown in FIG. 9, rotor-side ribs 2 m extending from the rotary case 3b toward the wheel 2 and wheel-side ribs 2 n extending from the wheel 2toward the above rotary case 3 b are interconnected by an elastic member15 at equal intervals in the circumferential direction of the wheel 2 sothat a shear spring having low stiffness in the vertical direction or acompression tension spring having high stiffness in the rotationdirection can be used as a spring for interconnecting the wheel 2 andthe inwheel motor 3. Therefore, the inwheel motor 3 can move only insubstantially the vertical direction, and the co-rotation of the inwheelmotor 3 and the wheel 2 can be further suppressed.

Alternatively, as shown in FIG. 10, a cylindrical elastic member 13R maybe used as the elastic member for interconnecting the wheel 2 and therotary case 3 b in place of the above second elastic member 13, one side13 h of the above elastic member 13R may be connected to the wheel 2,and the other side 13 m may be connected to the rotary case 3 b. Sincethe above cylindrical elastic member 13R functions as a shear springwhich is deformed in a shearing direction when it transmits the verticalmovement and torque of the inwheel motor 3, it has high stiffness in therotation direction and low stiffness in the radial direction, therebymaking it possible to improve rotation drive efficiency.

As shown in FIG. 11( a), the wheel 2 and the rotary case 3 b areinterconnected by a plurality of substantially board-like elasticmembers 13 a to 13 d arranged at equal intervals in parallel to thetangent direction of the wheel 2, whereby stiffness in the verticaldirection can be made low and stiffness in the rotation direction can bemade high. That is, when the end faces 13 w and 13 w in the widthdirection of the above board-like elastic members 13 a to 13 d aremounted to the wheel 2 to connect the wheel 2 to the rotary case 3 b,the board-like faces 13 s (faces perpendicular to the radial direction)of the above board-like elastic members 13 a to 13 d become parallel tothe rotation direction of the inwheel motor 3 or the wheel 2 so thatstiffness in the radial direction can be made low and stiffness in therotation direction can be made high. When the number of the aboveboard-like elastic members 13 a to 13 d is increased while their sizesare adjusted to maintain stiffness in the rotation direction, as shownin the graph of FIG. 12, stiffness in the vertical direction can bereduced.

The above stiffness in the vertical direction can be decomposed into avertical component of stiffness in the radial direction and a verticalcomponent of stiffness in the rotation direction. Therefore, to reducestiffness in the vertical direction, the vertical component of stiffnessin the radial direction and the vertical component of stiffness in therotation direction should be reduced. However, stiffness in the rotationdirection cannot be reduced in order to transmit the torque of the motorwithout a phase difference. Then, when rotary joint units 13 z and 13 zare provided on both end faces 13 w and 13 w in the width direction ofthe board-like elastic members 13 a to 13 d with the tangent directionof the motor as the axis to mount the above board-like elastic members13 a to 13 d to the wheel 2, stiffness in the radial direction iseliminated and stiffness in the vertical direction can be reducedwithout reducing stiffness in the rotation direction.

When the number of the above board-like elastic members 13 a to 13 d isincreased to maintain stiffness in the rotation direction, as shown inthe graph of FIG. 12, stiffness in the vertical direction alsoincreases. Therefore, the number of the above board-like elastic members13 a to 13 d is preferably 16 or less.

When the cylindrical elastic member 13R shown in FIG. 10 is used,stiffness in the vertical direction can also be reduced by providing theabove rotary joint units likewise to connect one end of the aboveelastic member 13R to the wheel 2.

As shown in FIG. 13, a connection portion with a drive shaft 9 may beformed in the hub portion 4 connected to the wheel 2 at its rotationaxis like a normal automobile to connect the hub portion 4 to the driveshaft 9. Thereby, power from a car power engine or motor other than theinwheel motor 3 can be transmitted to the wheel 2 by the above driveshaft 9 so that a hybrid car can be constructed by connecting the outputshaft of a gasoline engine vehicle to the hub portion 4 of the inwheelmotor system of the present invention.

Embodiment 2

In the above Embodiment 1, the rotary case 3 b and the wheel 2 areinterconnected by the second elastic member 13. As shown in FIG. 14 andFIG. 15, the above rotary case 3 b may be connected to the wheel 2 bythe second elastic member 13 and a constant-velocity universal joint 16.

That is, when the rotary case 3 b and the wheel 2 are interconnected byan elastic member as in the above Embodiment, a phase difference isproduced between the wheel 2 and the rotary case 3 b by sheardeformation in the circumferential direction. Therefore, the aboverotary case 3 b and the wheel 2 are interconnected by the above secondelastic member 13 and the constant-velocity universal joint 16. Byshifting the rotation center of a wheel-side joint 16 a from therotation center of a motor-side joint 16 b, the inwheel motor 3 cantransmit torque to the wheel 2 from the rotary case 3 b without a phasedifference while moving vertically in the wheel 2. Therefore, the abovephase difference can be minimized and the transmission efficiency oftorque from the rotary case 3 b to the wheel 2 can be improved.

Further, the non-rotary case 3 a and the knuckle 5 are interconnected bythe direct-acting guide unit 14 which comprises the damper 14 a and thesupport member 14 b shown in FIG. 7 and FIG. 8 of the above Embodiment 1to further reduce the above phase difference.

By mounting the second elastic member 13 at the center position of themass of the motor in the width direction of the motor, the mass of theinwheel motor 3 serves only as a counterweight, which prevents a partaround the wheel from sharing the mass of the motor.

When the non-rotary case 3 a and the knuckle 5 are interconnected by thefirst elastic member 11 as shown in FIG. 1 and not the abovedirect-acting guide unit 14, the above first elastic member 11 ispreferably mounted at the center position of the mass of the motor inthe width direction of the motor to prevent a part around the wheel fromsharing the mass of the motor.

Embodiment 3

In the above Embodiment 2, the rotary case 3 b and the wheel 2 areinterconnected by the second elastic member 13 and the constant-velocityuniversal joint 16. When the rotary case 3 b and the wheel 2 areinterconnected by a driving force transmitting unit which can beeccentric from the wheel 2 in the radial direction in place of the aboveconstant-velocity universal joint 16, torque transmission efficiencyfrom the rotary case 3 b to the wheel 2 can be further improved.

As the above driving force transmitting unit may be used, for example, aflexible coupling 18 which comprises a plurality of hollow disk-likeplates 18A to 18C and direct-acting guides 18 p and 18 q forinterconnecting the adjacent plates 18A and 18B and the adjacent plates18B and 18C and for guiding the adjacent plates 18A and 18B and theadjacent plates 18B and 18C in the radial direction of the disk as shownin FIGS. 16 to 18. The rotary case 3 b is connected to the wheel 2 bythe above flexible coupling 18 to minimize the phase difference betweenthe wheel 2 and the rotary case 3 b, thereby making it possible tofurther improve torque transmission efficiency from the rotary case 3 bto the wheel 2.

As shown in FIG. 19, for example, each of the above direct-acting guides18 p and 18 q comprises a guide rail 18 x having a projection extendingin the radial direction of the above plate, a guide member 18 y having arecess extending in the radial direction of the above plate and matingwith the above guide rail 18 x, and a plurality of steel balls 18 mplaced between the projection of the above guide rail 18 x and therecess of the guide member 18 y to slide the above guide rail 18 x andthe guide member 18 y smoothly.

The above guide rail 18 x and guide member 18 y are mounted on theopposing sides of the above adjacent plates 18A and 18B and the opposingsides of the above adjacent plates 18B and 18C, respectively.

Since the above guide rail 18 x and guide member 18 y slide such thatthey guide the above adjacent plates 18A and 18B and the adjacent plates18B and 18C in the radial direction of the disk, the inwheel motor 3 canmove in the working direction of the above direct-acting guides 18 p and18 q, that is, the radial direction of the disk but not in the rotationdirection. As a result, rotating torque can be transmitted to the wheel2 efficiently.

By providing two or more pairs of direct-acting guides 18 p and 18 qhaving different angles, the above inwheel motor 3 can transmit drivingtorque to the wheel 2 while it is eccentric from the shaft in anydirection.

When the number of direct-acting guides 18 p and 18 q is small, theangular velocity changes at the time of rotation. Therefore, a pluralityof plates and a plurality of direct-acting guides are preferablycombined. As shown in FIG. 18, when the number of the above hollowdisk-like plates is represented by N, the above plates 18A to 18C aredisposed to ensure that the angle formed by adjacent direct-actingguides should be incremented by 180/(N−1)° from the direct-acting guide18 p at one end, thereby making it possible to suppress a change in theabove angular velocity without fail (since N=3 in this embodiment, theabove angle is 90°).

Since the driving force of the inwheel motor 3 is transmitted to thewheel 2 mechanically when the rotary case 3 b and the wheel 2 areinterconnected by a driving force transmitting unit such as the aboveconstant-velocity universal joint 16 or the flexible coupling 18, onlythe first elastic member 11 interposed between the non-rotary case 3 aand the knuckle 5 suffices as a buffer member for exhibiting a dynamicdamper effect.

As the unit for guiding the above adjacent plates 18A to 18C in theradial direction of the disk may be used a flexible coupling 18Z asshown in FIGS. 20 to 22. This flexible coupling 18Z is constructed byforming bearing grooves 18 a to 18 c in the opposing sides of the aboveplates 18A to 18C in a radial direction and by placing bearing balls 18Mwhich are a steel ball and which can move along the bearing grooves 18 aand 18 b and 18 b and 18 c between the opposing hollow disk-like plates18A and 18B and between the opposing hollow disk-like plates 18B and18C, respectively. A combination of the above bearing grooves 18 a and18 b and a combination of the above bearing grooves 18 b and 18 c eachconstitute a direct-acting guide together with the bearing ball 18M.

That is, as the above bearing grooves 18 a to 18 c are formed such thatthe bearing balls 18M roll in the radial directions of the above plates18A to 18C, the inwheel motor 3 can move in the direction of the abovebearing grooves 18 a to 18 c but not the circumferential direction,thereby making it possible to transmit rotating torque to the wheel 2efficiently. By combining two or more pairs of bearing grooves 18 a to18 c having different angles with the bearing balls 18M, the aboveinwheel motor 3 can transmit driving torque to the wheel 2 while it iseccentric from the shaft in any direction.

Since the angular velocity changes at the time of rotation when thenumber of the bearing grooves is small, it is preferred to combine aplurality of plates with the bearing balls. Like the above direct-actingguides, as shown in FIG. 22, when the number of the above plates isrepresented by N, the above hollow disk-like plates are disposed toensure that the angle formed by adjacent grooves in the axial directionof the plates should be incremented by 180/(N−1)° from the groove at oneend, thereby making it possible to suppress a change in the aboveangular velocity without fail.

The plate 18A on the wheel 2 side (or the plate 18A and the guide rail18 x) which is a plate at one end may be integrated with the wheel 2 orthe plate 18C on the rotary case 3 b side (or the plate 18C and theguide member 18 y) may be integrated with the rotary case 3 b in theabove flexible couplings 18 and 18Z. In this case, the number N of theplates used for the calculation of the angle is a value based on theassumption that there are plates at both ends.

Embodiment 4

In the above Embodiment 3, the flexible coupling 18 which compriseshollow disk-like plates 18A to 18C having direct-acting guides 18 p and18 q on front and back sides disposed in crossing directions is used asthe driving force transmitting unit for interconnecting the rotary case3 b and the wheel 2. A flexible coupling 19, which comprises (1) ahollow disk-like plate 20A located on the wheel 2 side and connected tothe wheel 2, (2) a hollow disk-like plate 20C located on the motor 3side and connected to the rotary case 3 b of the motor 3, and (3) ahollow disk-like plate 20B having a plurality of direct-acting guides19A and 19B at the same positions on the front and back sides of themotor 3 side plate and the wheel 2 side plate at intervals of 90° or180° in the circumferential direction of the plates and connected to theabove hollow disk-like plate 20A by the direct-acting guide 19A and tothe above hollow disk-like plate 20C by the direct-acting guide 19B asshown in FIG. 23 and FIG. 24, may be used to interconnect the rotarycase 3 b and the wheel 2. Thereby, compression and tensile forcegenerated in the circumferential direction of the plates are canceledeach other to enable the elimination of an offset in the circumferentialdirection, the transmission of driving torque from the inwheel motor 3to the wheel 2 with more certainty and the improvement of the durabilityof the driving force transmitting unit.

In this embodiment, the working direction of the direct-acting guide 19Blocated on the motor 3 side is 45° from the radial direction of thehollow disk-like plates 20A to 20C and the working direction of thedirect-acting guide 19A located on the wheel 2 side is perpendicular tothe working direction of the above direct-acting guide 19B.

In this embodiment, the non-rotary case 3 a and the knuckle 5 areinterconnected by a direct-acting guide unit 21 which comprises adirect-acting guide member 21 a for guiding the above non-rotary case 3a in the vertical direction of the vehicle and a shock absorber 21 bconsisting of a damper and a spring member expanding and contracting inthe working direction of this direct-acting guide member 21 a. Thenon-rotary case 3 a and the knuckle 5 may be interconnected by a buffermember such as the direct-acting guide unit 14 having the damper 14 a asshown in FIG. 7 and FIG. 8 of the above Embodiment 1. Since the rotarycase 3 b and the wheel 2 are interconnected by the above driving forcetransmission unit in this embodiment like the above Embodiments 2 and 3,the second elastic member 13 interposed between the rotary case 3 b andthe wheel 2 can be omitted.

A description is subsequently given of the locations of thedirect-acting guides 19A and 19B.

Each of the direct-acting guides 19A consists of a guide member 19 a anda guide rail 19 b as shown in FIG. 24. In this embodiment, four guidemembers 19 a having a recess extending at 45° from the radial directionare disposed at intervals of 90° in the circumferential direction of thehollow disk-like plate located on the wheel 2 side (to be referred to as“wheel-side plate” hereinafter), and four guide rails 19 b having aprojection to be engaged with the above guide members 19 a are disposedat positions corresponding to the above guide members 19 a of theintermediate hollow disk-like plate (to be referred to as “intermediateplate” hereinafter) to interconnect the wheel-side plate 20A and theintermediate plate 20B by the four direct-acting guides 19A disposed atintervals of 90°.

Each of the direct-acting guides 19B consists of a guide rail 19 c and aguide member 19 d. Four guide rails 19 c are disposed at intervals of90° perpendicular to the guide rails 19 b of the above direct-actingguides 19A in the circumferential direction on the motor 3 side hollowdisk-like plate (to be referred to as “motor-side plate” hereinafter)side of the intermediate plate 20B, and four guide members 19 d aredisposed at positions corresponding to the guide rails 19 c in thecircumferential direction of the motor-side plate 20C to interconnectthe intermediate plate 20B and the motor-side plate 20C by the fourdirect-acting guide 19B disposed at intervals of 90°.

In the above constitution, when torque is transmitted from the rotarycase 3 b of the inwheel motor 3 to the wheel-side plate 20A connected tothe wheel 2 through the motor-side plate 20C, the above direct-actingguides 19A and 19B are disposed at 45° from the axial direction of thehollow disk-like plates 20A to 20C. Therefore, as shown in FIG. 25,circumferential-direction rotating force and radial-direction expandingforce are applied to the above intermediate plate 20B. However, sincethe direct-acting guides 19A which move in a direction perpendicular tothe working direction of the direct-acting guides 19B are disposed onthe back side (wheel 2 side) of the direct-acting guides 19B of theabove intermediate plate 20B, that is, at the same positions as theabove direct-acting guides 19B, force for expanding the aboveintermediate plate 20B in the radial direction is balanced with theradial-direction expanding force of the above direct-acting guides 19Awith the result that only torque is transmitted to the wheel-side plate20A and to the wheel 2. Therefore, as torque input into thedirect-acting guides 19B from the motor-side plate 20C connected to therotary case 3 b is transmitted to the wheel-side plate 20A through theabove intermediate plate 20B therebetween, the driving force of theabove motor 3 can be transmitted to the wheel 2 without fail.

Since the working directions of the above direct-acting guides 19A and19B are the same, compression and tensile stress are not generated inthe hollow disk-like plates 19A to 19C at the same time and only forcefor expanding or contracting all of them in the radial direction isapplied to them. Compression and tensile stress are not generated in thedirect-acting guides 19B at the same time as the working direction ofall the direct-acting guides 19B is perpendicular to the workingdirection of the above direct-acting guides 19A. Since the aboveexpansion or compression force is transmitted from the both sides of theguide rails 19 b and 19 c sandwiching the intermediate plate 19B, thereis no offset of a load in the circumferential direction of theintermediate disk plate 20B, thereby reducing the risk of buckling.

Embodiment 5

A flexible coupling 20 as shown in FIG. 26 and FIG. 27, which comprises(1) a hollow disk-like plate (wheel-side plate) 20A located on the wheelside and connected to the wheel 2, (2) a hollow disk-like plate(motor-side plate) 20C located on the motor side and connected to therotary case 3 b of the motor 3, (3) a first hollow disk intermediateplate 20M having a plurality of direct-acting guides 19P and 19Q at thesame positions on the front and back sides of the motor 3 side plate andthe wheel 2 side plate at intervals of 90° or 180° in thecircumferential direction of the plates and connected to the abovewheel-side plate 20A by the direct-acting guides 19P and to the abovemotor-side plate 20C by the direct-acting guides 19Q, and (4) a secondhollow disk intermediate plate 20N arranged on the inner side of thefirst intermediate plate 20M, having a plurality of direct-acting guides19R and 19S arranged in an opposite way to that of the firstintermediate plate 20M and connected to the above wheel-side plate 20Aby the direct-acting guides 19R and to the above motor-side plate 20C bythe direct-acting guides 19S, may be used in place of the flexiblecoupling 18 of the above Embodiment 3 to interconnect the rotary case 3b and the wheel 2. Thereby, vibration caused by the eccentric rotationof the above plates can be reduced, and driving torque can betransmitted from the inwheel motor 3 to the wheel 2 without fail.

In this embodiment, like the above Embodiment 4, the non-rotary case 3 aand the knuckle 5 are interconnected by the direct-acting guide unit 21which comprises the direct-acting guide member 21 a for guiding thenon-rotary case 3 a in the vertical direction of the vehicle and theshock absorber 21 b consisting of a damper and a spring member expandingand contracting in the working direction of the direct-acting guidemember 21 a.

The locations of the above direct-acting guides 19P and 19Q and thedirect-acting guides 19R and 19S will be described hereinunder.

The direct-acting guide 19P consists of guide members 19 i and guiderails 19 j as shown in FIG. 27. In this embodiment, the direct-actingguide 19P consists of (1) two guide members 19 i and 19 i having arecess extending in the radial direction of the above first intermediateplate 20M and disposed on the first intermediate plate 20M side of thewheel-side plate 20A located on the wheel 2 side at an interval of 180°in the circumferential direction and (2) two guide rails 19 j and 19 jhaving a projection to be engaged with the above guide members 19 i and19 i and disposed at positions corresponding to the above guide members19 i and 19 i in the circumferential direction on the wheel-side plate20A side of the first intermediate plate 20M. This direct-acting guide19P guides the wheel-side plate 20A and the first intermediate plate 20Min the radial direction of the plates.

The direct-acting guide 19Q consists of (1) two guide rails 19 p and 19p provided on the motor-side plate 20C side of the first intermediateplate 20M at an interval of 180° at positions 90° from the above guiderails 19 j and 19 j in the circumferential direction and (2) two guidemembers 19 q and 19 q disposed at positions corresponding to the aboveguide rails 19 p and 19 p in the circumferential direction of themotor-side plate 20C. This direct-acting guide 19Q guides the motor-sideplate 20C and the first intermediate plate 20M in the radial directionof the disk.

Meanwhile, the direct-acting guide 19R consists of two guide members 19m and 19 m having a recess extending in the radial direction of theabove wheel-side plate 20A and disposed on the inner side in the radialdirection of the above guide members 19 i and 19 i at an interval of180° at positions 90° from the above guide members 19 i and 19 i in thecircumferential direction, and two guide rails 19 n and 19 n having aprojection to be engaged with the above guide members 19 m and 19 m anddisposed on the wheel-side plate 20A side of the second intermediateplate 20N at positions corresponding to the above guide members 19 m and19 m in the circumferential direction. The direct-acting guide 19Sconsists of two guide rails 19 r and 19 r disposed at an interval of180° at positions 90° from the above guide rails 19 n and 19 n in thecircumferential direction on the motor-side plate 20C side of the secondintermediate plate 20N and two guide members 19 s and 19 s having arecess to be engaged with the above guide rails 19 r and 19 r anddisposed at positions corresponding to the above guide rails 19 r and 19r in the circumferential direction of the motor-side plate 20C.

Owing to the above constitution, the motor 3 turns while it is eccentricfrom the wheel 2 in a downward direction. Stated more specifically,motor torque is first applied to the motor-side plate 20C and thiscircumferential direction force applied to the motor-side plate 20C isapplied to the first intermediate plate 20M through the direct-actingguide 19Q and further to the second intermediate plate 20N through thedirect-acting guide 19S which operates in a direction perpendicular tothe above direct-acting guide 19Q.

The circumferential direction force applied to the above firstintermediate plate 20M is applied to the wheel-side plate 20A throughthe direct-acting guide 19P and circumferential direction force appliedto the above second intermediate plate 20N is applied to the wheel-sideplate 20A through the direct-acting guide 19R which operates in adirection perpendicular to the above direct-acting guide 19P.

Therefore, for example, when the motor 3 turns clockwise while it iseccentric from the wheel 2 in a downward direction as shown in FIGS. 28(a) to (c), the first intermediate plate 20M on the outer side turnsclockwise from down to left and up eccentrically with the center pointbetween the axis of the wheel-side plate 20A and the axis of themotor-side plate 20C as the center. Meanwhile, the second intermediateplate 20N on the inner side turns clockwise from up to right and downeccentrically with the center point between the axis of the wheel-sideplate 20A and the axis of the motor-side plate 20C as the center.

When the mass of the above second intermediate plate 20N is made equalto the mass of the first intermediate plate 20M, the above first andsecond intermediate plates 20M and 20N turn eccentrically indot-symmetrical directions as described above, whereby vibrations causedby their eccentricities are canceled each other, the motor-side plate20C and the wheel-side plate 20A become eccentric from each other onlyin the vertical direction and not the longitudinal direction. Therefore,vibrations caused by the eccentric rotations of the hollow disk-likeplates (plates 20A, 20M, 20N, 20C) can be reduced and driving force canbe transmitted to the wheel 2 without fail.

When direct-acting guides 22P and 22Q and direct-acting guides 22R and22S whose working directions are 45° from the radial directions of theplates 20A, 20M, 20N and 20C are mounted at the same positions on thefront and back sides of the above first and second intermediate plates20M and 20N in place of the above direct-acting guides 19P and 19Q andthe direct-acting guides 19R and 19S as shown in FIG. 29, compressionand tensile stress are not generated in the above hollow disk-likeplates 20A, 20M, 20N and 20C at the same time like the above Embodiment4, only force for expanding or compressing the whole in the radialdirection is applied, and the working directions of the direct-actingguides 22Q and 22S are perpendicular to the working directions of theabove direct-acting guides 22P and 22R, thereby making it possible toprevent compression and tensile stress from being generated at the sametime. Therefore, there is no offset of load in the circumferentialdirections of the above first and second intermediate plates 20M and20N, the risk of buckling is reduced, and the durability of the drivingforce transmission unit can be improved.

The direct-acting guide 22P consists of a guide member 22 a and a guiderail 22 b, the direct-acting guide 22Q consists of a guide rail 22 c anda guide member 22 d, the direct-acting guide 22R consists of a guidemember 22 e and a guide rail 22 f, and the direct-acting guide 22Sconsists of a guide rail 22 g and a guide member 22 h. The guide members22 a and the guide members 22 e are provided on the wheel-side plate 20Alike the above Embodiment 4. The guide rails 22 b are provided on thewheel-side plate 20A side of the first intermediate plate 20M, the guiderails 22 c on the motor-side plate 20C side of the first intermediateplate 20M, the guide rails 22 f on the wheel-side plate 20A side of thesecond intermediate plate 20N, the guide rails 22 g on the motor-sideplate 20C side of the second intermediate plate 20N, and the guidemembers 22 d and the guide members 22 h on the wheel-side plate 20C.

Embodiment 6

In the above Embodiments 1 to 5, the non-rotary case 3 a of the inwheelmotor 3 and the knuckle 5 which is a part around the wheel of thevehicle are interconnected by a buffer member such as the first elasticmember 11 or the direct-acting guide unit 21 which comprises thedirect-acting guide member 21 a and the shock absorber 21 b consistingof a spring member expanding and contracting in the working direction ofthe direct-acting guide member 21 and the damper. By interconnecting thenon-rotary case 3 a and the knuckle 5 by buffer units 23A and 23B havingone end connected to the knuckle 5 and the other end supporting themotor 3 as shown in FIG. 30, TCFF can be further reduced.

In this embodiment, the rotary case 3 b and the wheel 2 areinterconnected by the flexible coupling 18 used in the above Embodiment3. However, the driving force transmission unit such as theconstant-velocity universal joint 16 of the above Embodiment 2 or theflexible coupling 19 or 20 of the above Embodiment 5 or 6 may be used tointerconnect these.

The above buffer units 23A and 23B may be substantially A-shaped orH-shaped link units, each comprising two arms 23 m and 23 n which areinterconnected rotatably by a buffer member 23 k consisting of a springand/or a damper at a junction 23Z. In this embodiment, one end of thebuffer member 23 k is fixed to an attachment member 23 s attached to theabove arm 23 m and the other end is directly attached to the above arm23 n. Both ends of the buffer member 23 k may be directly attached tothe arms 23 m and 23 n, respectively.

To connect the above buffer units 23A and 23B to the non-rotary case 3 aof the inwheel motor 3 and the knuckle 5, the end portions 23X of thearms 23 m of the above buffer units 23A and 23B are attached to thenon-rotary case 3 a of the above motor 3 and the end portions 23Y of theother arms 23 n are attached to the knuckle 5. At this point, the abovebuffer units 23A and 23B are attached such that the expansion orcontraction direction of the above buffer member 23 k becomes thevertical direction of the vehicle. Since the changing direction of theconnection point 23X with the non-rotary case 3 a of the above arm 23 mand the changing direction of the connection point 23Y with the knuckle5 of the above arm 23 n are thereby limited to the expansion orcontraction direction of the above buffer member 23 k comprising aspring or damper, the non-rotary case 3 a and the knuckle 5 can beinterconnected in such a manner that they can move in the verticaldirection of the motor 3.

That is, in this embodiment, the rotary case 3 b for fixing the rotor 3Rof the inwheel motor 3 and the wheel 2 are interconnected by theflexible coupling 18 (or the flexible coupling 19 or 20), and thenon-rotary case 3 a for fixing the stator 3S is fixed to the knuckle 5which is a part around the wheel of the vehicle in the rotationdirection and elastically supported in the vertical direction.Therefore, torque transmission efficiency from the rotary case 3 b tothe wheel 2 can be improved, TCFF can be further reduced, and the roadholding properties of the vehicle can be enhanced.

Embodiment 7

In the above Embodiment 6, the buffer units 23A and 23B which aresubstantially A-shaped or H-shaped link units, each comprising two arms23 m and 23 n interconnected by the buffer member 23 k, are used tointerconnect the non-rotary case 3 a of the inwheel motor 3 and theknuckle 5 which is a part around the wheel of the vehicle. When avehicle equipped with the inwheel motor 3 has a shaft type suspensionunit, as shown in FIG. 31, a buffer unit 24 similar in construction tothe above buffer units 23A and 23B is used to interconnect thenon-rotary case 3 a and a shaft 9J, thereby making it possible to reduceTCFF.

The above buffer unit 24 is a substantially H-shaped or A-shaped linkunit which comprises two arms 24 m and 24 n rotatably connected to theshaft 9J by buffer members 24 k consisting of a spring or damper. Inthis embodiment, the two arms 24 m and 24 n are rotatably connected tothe shaft 9J by the two buffer members 24 k and 24 k having one endconnected to the shaft 9J so that the expansion or contraction directionbecomes the vertical direction of the vehicle. The above buffer members24 k and 24 k may be attached to the arms 24 m and 24 n by an attachmentmember 24 s or directly.

Thereby, even in the vehicle having a shaft suspension unit, thenon-rotary case 3 a and the knuckle 5 can be interconnected such thatthey can move in the vertical direction of the motor 3, thereby makingit possible to further reduce TCFF.

Embodiment 8

FIG. 32 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 8. In the figure, reference numeral 1 denotes atire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b, 3denotes an inwheel motor of an outer rotor type, 4 denotes a hub portionconnected to the above wheel 2 at its rotation axis, 5 denotes a knucklewhich is a part around the wheel of a vehicle and connected to a shaft9J, 7 denotes a suspension member composed of a shock absorber or thelike, 8 denotes a brake mounted to the above hub portion 4, 18 denotes aflexible coupling shown in FIGS. 16 to 18 of the above Embodiment 3which comprises hollow disk-like plates having a plurality ofdirect-acting guides on the front and back sides in such a manner thatthe working directions thereof are perpendicular to each other and whichis used to interconnect the rotary case 3 b for supporting the rotor 3Rof the inwheel motor 3 and the wheel 2 in such a manner that they can beeccentric from each other in the radial direction of the wheel 2, and 25denotes a buffer unit for elastically supporting the non-rotary case 3 awhich supports the stator 3S of the inwheel motor 3 to the knuckle 5 inthe vertical direction of the vehicle. The rotary case 3 b and the wheel2 may be interconnected by the driving force transmission unit such asthe constant-velocity universal joint 16 of the above Embodiment 2 orthe flexible coupling 19 or 20 of the above Embodiment 5 or 6 in placeof the above flexible coupling 18.

As shown in FIG. 33, the above buffer unit 25 comprises two plates 25Aand 25B interconnected by springs 25 b which operate in the verticaldirection of the vehicle and whose working directions are limited to thevertical direction of the vehicle by direct-acting guides 25 a anddampers 25 c. In this embodiment, four springs 25 b which expand andcontract in the vertical direction of the vehicle are mounted at thefour corners of the plate 25B located on the suspension member 7 side(to be referred to as “knuckle attachment plate” hereinafter) andconnected to the shaft 9J linked to the knuckle 5, two dampers 25 cwhich expand and contract in the vertical direction of the vehicle areprovided on both sides of a connection hole 25 m for the shaft 9J formedin the center portion thereof, spring receiving portions 25 d areprovided at respective positions corresponding to the top and bottomportions of the above springs 25 b of the plate 25A located on the motor3 side (to be referred to as “motor attachment plate” hereinafter), adamper attachment portion 25 e is provided at a position correspondingto the top portion of the above dampers 25 c, that is, above aconnection hole 25 n for the shaft 9J, and the above plates 25A and 25Bare interconnected by the four direct-acting guides 25 a symmetricalabout the center of the plate.

Since the above motor attachment plate 25A and the knuckle attachmentplate 25B are guided in the vertical direction of the vehicle by theabove four direct-acting guides 25 a and interconnected by the springs25 b and the dampers 25 c, they can confine the inwheel motor 3 in thevertical movement direction while they generate attenuation force.

In this Embodiment 8, as the rotary case 3 b for fixing the rotor 3R ofthe inwheel motor 3 and the wheel 2 are interconnected by the flexiblecoupling 18, and the non-rotary case 3 a for supporting the stator 3S isconnected in such a manner that it is fixed in the rotation direction ofthe wheel 2 (or the shaft 9J) and it can move in the vertical directionof the vehicle, torque transmission efficiency from the rotary case 3 bto the wheel 2 can be improved, TCFF can be reduced, and the roadholding properties of the vehicle can be improved.

Embodiment 9

In the above Embodiment 8, the plates 25A and 25B are interconnected bythe direct-acting guides 25 a, springs 25 b and dampers 25 c. As shownin FIG. 34 and FIG. 35, the non-rotary case 3 a for supporting thestator 3S can be fixed in the rotation direction of the wheel 2 (or theshaft 9J) with more certainty and connected such that it can move in thevertical direction of the vehicle by using a buffer unit 30 whichcomprises hydraulic cylinders 26 and reservoir tanks 29 connected to thehydraulic cylinders 26 by pressure hoses 27 and 28 in place of the abovedampers 25 c and 25 c, thereby making it possible to further reduceTCFF.

FIG. 36 shows the details of the above buffer unit 30 comprisinghydraulic cylinders. In this embodiment, each of the above reservoirtanks 29 consists of an expansion-side reservoir tank 29A whichcommunicates with the upper chamber 26 a of the hydraulic cylinder 26and a contraction-side reservoir tank 29B which communicates with thelower chamber 26 b of the hydraulic cylinder 26, these chambers 26 a and26 b are separated from each other by a piston 26P to which one end of apiston rod 26L is fixed, the upper chamber 26 a of the above hydrauliccylinder 26 and the expansion-side reservoir tank 29A are interconnectedthrough an expansion-side valve (orifice) 27 m, and the lower chamber 26b and the contraction-side reservoir tank 29B are interconnected througha contraction-side valve (orifice) 28 m. 27 n and 28 n denote anexpansion-side check valve and a contraction-side check valve forpreventing a backflow of working oil 29 s into the hydraulic cylinder 26from the reservoir tank 29, which are provided in oil branch lines 27 kand 28 k bypassing the above expansion-side valve 27 m and thecontraction-side valve 28 m, respectively.

In this embodiment, as shown in FIG. 35, only the simple-structuredhydraulic cylinders 26 are mounted on the knuckle attachment plate 25Bconnected to the knuckle 5 which is a part around the wheel, and thereservoir tanks 29 for securing a flow rate of working oil 29 s forgenerating attenuation force are mounted at positions other than aposition around the wheel (on the unshown car body side of the shaft9J).

The buffer unit 30 of this embodiment has an advantage that attenuationforce on the expansion side of the buffer unit and attenuation force onthe contraction side of the buffer unit can be separately adjustedbecause the piston upper chamber 26 a and the piston lower chamber 26 bof the hydraulic cylinder 26 are connected to the reservoir tanks 29Aand 29B by the pressure hoses 27 and 28 through the separate valves 27 mand 28 m, respectively.

When the piston upper chamber 26 a and the piston lower chamber 26 b ofthe hydraulic cylinder 26 are connected to the separate valves 27 m and28 m, respectively, and the both lines are connected to a commonreservoir tank 29C as shown in FIG. 37, or when the piston upper chamber26 a and the piston lower chamber 26 b of the hydraulic cylinder 26 areconnected by the separate valves 27 m and 28 m, and the piston lowerchamber 26 b and the reservoir tank 29C are interconnected as shown inFIG. 38, the number of parts of the buffer unit 30 can be reduced andthe buffer unit 30 can be reduced in size.

Embodiment 10

FIG. 39 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 10 and FIG. 40 is a sectional view of its keysection. In these figures, reference numeral 1 denotes a tire, 2 denotesa wheel consisting of a rim 2 a and a wheel disk 2 b, and 3I denotes ahollow inner rotor type motor (inwheel motor) which comprises a stator3S fixed to a non-rotary case 3 a provided on the outer side in theradial direction and a rotor 3R fixed to a rotary case 3 b rotatablyconnected to the above non-rotary case 3 a through a bearing 3 j andprovided on the inner side in the radial direction.

Reference numeral 4 represents a hub portion connected to the abovewheel 2 at its rotation axis, 5 represents a knuckle connected to upperand lower suspension arms 6 a and 6 b, 7 represents a suspension memberwhich is a shock absorber or the like, and 8 represents a brake which isa brake disk comprising a brake rotor 8 a and a brake caliper 8 b andmounted to the above hub portion 4.

In this embodiment, the non-rotary case 3 a which is the outer case ofthe above inwheel motor 3I and the knuckle 5 which is a part around thewheel are interconnected by a direct-acting guide unit 21 whichcomprises a direct-acting guide member 21 a for guiding the abovenon-rotary case 3 a in the vertical direction of the vehicle and a shockabsorber 21 b consisting of a spring member expanding and contracting inthe working direction of the direct-acting guide member 21 a and adamper, and the rotary case 3 b which is the inner case of the abovemotor 3I and the wheel 2 are interconnected by the flexible coupling 18which comprises hollow disk-like plates 18A to 18C having a plurality ofdirect-acting guides 18 p and 18 q on the front and back sides so thatthe working directions thereof become perpendicular to each other asshown in FIGS. 16 to 18 of the above Embodiment 3. The rotary case 3 bfor supporting the rotor 3R of the inwheel motor 3I and the wheel 2 areinterconnected by the above flexible coupling 18 in such a manner thatthey can be eccentric from each other in the radial direction of thewheel 2.

One end of a connection member 21 t having an L-shaped section is fixedto the side opposite to the wheel 2 of the non-rotary case 3 a and theother end is fixed to the upper end of the above direct-acting guideunit 21 having a lower end secured to the knuckle 5.

In this Embodiment 10, since the above non-rotary case 3 a is connectedto the knuckle 5 by the direct-acting guide unit 21 which comprises thedirect-acting guide member 21 a for guiding the above non-rotary case 3a in the vertical direction of the vehicle and the shock absorber 21 bconsisting of a spring member expanding and contracting in the workingdirection of the direct-acting guide member 21 a and a damper, and theinwheel motor 3I can be float mounted to an unsprung mass correspondingportion which is a part around the wheel of the vehicle as describedabove, the axis of the motor and the axis of the wheel can moveseparately in the radial direction. Therefore, the mass of the motor isseparated from the unsprung mass of the vehicle and functions as theweight of a so-called dynamic damper.

Since the weight of the dynamic damper cancels unsprung vibration at thetime of running over an uneven road, TCFF is reduced with the resultthat the road holding properties of the vehicle are improved, vibrationapplied to the motor 3I can be reduced at the time of running over a badroad and accordingly, a load on the motor 3I imposed by vibration can bereduced.

Since the rotary case 3 b of the inwheel motor 3I and the wheel 2 areinterconnected by the flexible coupling 18, the inwheel motor 3I canmove in the working direction of the direct-acting guides 18 p and 18 qof the flexible coupling 18, that is, the radial direction of the hollowdisk-like plates 18A to 18C but not in the rotation direction because itis restricted by the above direct-acting guides 18 p and 18 q.Therefore, torque from the rotor 3R can be transmitted to the wheel 2efficiently.

Although the axis of the motor and the axis of the wheel becomeeccentric from each other by the vibration of the motor at the time ofrunning over a bad road, torque can be transmitted smoothly by using theabove flexible coupling 18.

The transmission efficiency of driving force can be further improved byusing a driving force transmission unit such as the flexible coupling 19or 20 of the above Embodiment 4 or 5 in place of the above flexilecoupling 18.

Even in the inwheel motor system of the present invention, as the massof the vehicle is supported by the hub portion 4, a load on the body ofthe motor 3I is small. Therefore, since a change in the air gap betweenthe rotor 3R and the stator 3S can be made small, the stiffness of thecase can be lowered, and the weight of the motor 3 can be therebyreduced.

When the outer rotor type motor is used in the present invention, thebearing of the rotation portion on the outer race side turns. When themotor runs at a high speed, the outer race is expanded outward in theradial direction by the centrifugal force of the motor, causing thedislocation of the bearing which is not preferred in terms ofdurability.

Therefore, as the bearing on the inner race side turns when the innerrotor type motor whose inner side turns is used, the inner race expandsin the radial direction at the time of high-speed rotation, and thedislocation of the bearing does not occur accordingly. Since the innerrotor type motor is smaller in the radius of a rotation portion than theouter rotor type motor, inertia moment can be made small and response tothe operation of the accelerator can be improved, thereby making itpossible to realize an inwheel motor car having excellent runningstability.

EXAMPLE 1

The vibration level of the inwheel motor system according to Embodiment1 is analyzed based on car vibration models as shown in FIGS. 41 to 43and the table of FIG. 44 at the time of running over an uneven road andthe results of comparison with the level of TCFF in the system of theprior art are shown in the graph of FIG. 45.

In FIG. 45, the horizontal axis shows vibration frequency (Hz) and thevertical axis shows the level (N) of TCFF. Comparative Example 1-1 is acar vibration model without an inwheel motor.

Since the inwheel motor is directly mounted to an unsprung masscorresponding portion such as a wheel or knuckle in the system of theprior art, its car vibration model is expressed as a two-freedomvibration model as shown in FIG. 41 (Comparative Example 1-2).Describing in detail, a vibration model in which the unsprung mass m₁ isconnected to the contact face R of the tire by an elastic member k₁ anda dash pot c₁ and in which the above unsprung mass m₁ and the sprungmass m₂ are interconnected by an elastic member K₂ and a dash pot C₂ maybecome a model in which the mass of the inwheel motor is added to theabove unsprung mass m₁. When the motor is directly mounted, the level ofTCFF rises due to an increase in the unsprung mass. Since the tire has anon-linear vertical load as shown in FIG. 46, if TCFF is large,capability such as the cornering power of the tire lowers and the roadholding properties of the vehicle deteriorate. To maintain these at thelevel of the above Comparative Example 1-1, the total weight of themotor and the part around the wheel must be made equal to that of theprior art system. However, in order to greatly reduce the weight of thepart around the wheel while the requirement for strength is satisfied, aserious cost rise is expected due to use of a large amount of a lightalloy, which cannot be said to be practical.

Meanwhile, to reduce the level of a load change at the time of runningover an uneven road without reducing the weight of the part around thewheel, there is a method called “dynamic damper”. As shown in FIG. 42,this dynamic damper is represented by a three-freedom model (ComparativeExample 1-3) in which new mass m₃ is added to the above two-freedommodel shown in FIG. 41 by an elastic member k₃ and a dash pot C₃.According to this method, the level of TCFF can be lowered withoutreducing the weight. However, although the effect of reducing the changeimproves more as the weight increases in the above dynamic damper, thisadditional weight has a bad influence such as a weight increase on thevehicle. Therefore, the above weight cannot be increased and accordinglythere is limitation to the effect of reducing the change.

In contrast to this, since the inwheel motor is connected to the partaround the wheel (unsprung mass) by the elastic member, or the elasticmember and the guide unit as shown in FIG. 1 and FIG. 7 or FIG. 39 inthe inwheel motor system of the present invention, the car vibrationmodel can be represented by a three-freedom model in which the weight ofthe dynamic damper is equivalent to the mass m₃ of the above inwheelmotor (Example 1-1).

Therefore, as shown in the graph of FIG. 45, the change level can bereduced without increasing the weight of the vehicle excessively.

At this point, the level of TCFF can be reduced without fail byadjusting the mass m₃ of the inwheel motor and the elastic constant k₃of the elastic member for connecting an unsprung part to ensure that theresonance frequency f₃ of the above mounted inwheel motor should behigher than the resonance frequency f₂ of sprung mass and lower than theresonance frequency f₁ of unsprung mass as shown in the expressionbelow.

$\begin{matrix}\begin{matrix}{f_{2} < f_{3} < f_{1}} & \; & \; \\{f_{1} = {\frac{1}{2\;\pi}\sqrt{\frac{m_{1}}{k_{1}}}}} & {\mspace{11mu}{f_{2} = {\frac{1}{2\;\pi}\sqrt{\frac{m_{2}}{k_{2}}}}}} & {\mspace{11mu}{f_{3} = {\frac{1}{2\;\pi}\sqrt{\frac{m_{3}}{k_{3}}}}}}\end{matrix} & \left\lbrack {{expression}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the above constitution, the motor and the part around the wheel canbe made lightweight like Example 1-2, the elastic constant of theelastic member can be reduced like Example 1-3, and when the both arecombined like Example 4, the change level can be further reduced (seethe table of FIG. 44 and the graph of FIG. 46).

Embodiment 11

FIG. 47 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 11. In FIG. 47, reference numeral 1 denotes atire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b,and 3 denotes an inwheel motor of an outer rotor type which comprises astator 3S fixed to a non-rotary case 3 a and a rotor 3R fixed to arotary case 3 b rotatably connected to the above non-rotary case 3 athrough a bearing 3 j and provided on the outer side in the radialdirection.

Reference numeral 4 represents a hub portion connected to the wheel 2 atits rotation axis, 5 represents a knuckle which is a part around thewheel of the vehicle and connected to suspension arms 6 a and 6 b, 7 asuspension member, and 8 represents a brake.

In Embodiment 11, the non-rotary case 3 a of the inwheel motor 3 isconnected to the knuckle 5 which is a part around the wheel of thevehicle, the rotary case 3 b rotatably connected to the above non-rotarycase 3 a through the bearing 3 j is connected to the rotating wheel 2 insuch a manner that it is inscribed in the wheel 2, and the hub portion 4connected to the above wheel 2 at its rotation axis and the knuckle 5are coupled through a hub bearing 31 provided on the inner side of thehollow inwheel motor 3 so that the weight of the vehicle can be sharedby the wheel 2 and a motor case 3C consisting of the above non-rotarycase 3 a, the bearing 3 j and the rotary case 3 b.

That is, since the weight of the vehicle can be shared by the wheel 2and the motor case 3C in a ratio of “stiffness of the wheel includingthe stiffness of the hub bearing” and “stiffness of the motor case” byemploying the above structure, the weight of the vehicle for each wheelis shared by the motor case 3 c and the hub bearing 31. Thereby, a loadon the motor case 3C is reduced and a change in the air gap 3 g betweenthe rotor 3R and the stator 3S can be reduced, whereby the weight of theinwheel motor 3 can be reduced by lowering the stiffness of the motorcase 3C or by reducing the size of the motor itself. Accordingly, as theunsprung vibration level and sprung vibration level of the vehicle canbe reduced, the riding comfort of the vehicle can be improved.

As the rotary case 3 b which is an outer case is connected to the wheel2 in such a manner that it is inscribed in the wheel 2 in thisembodiment, torque can be transmitted from the inwheel motor 3 to thewheel 2. Further as the brake 8 is mounted to the hub portion 4, braketorque is transmitted only to the above hub portion 4 and the knuckle 5at the time of braking, and brake reaction is not applied to the motorcase 3C. Therefore, the stiffness of the motor case 3C can be lowered,thereby making it possible to further reduce the weight of the inwheelmotor 3.

By connecting the rotary case 3 b to the wheel 2 by an elastic member 32as shown in FIG. 48, the distortion of the motor case 3C can be furtherreduced.

That is, as the wheel 2 turns while it is distorted by stress in variousdirections received from the surface of a road, the distortion of themotor case 3C can be reduced by absorbing the deformation of this wheel2 with the above elastic member 32. Therefore, the stiffness of themotor case 3C can be further lowered and the weight of the inwheel motor3 can be reduced. Since the rotary case 3 b and the wheel 2 areinterconnected by the elastic member 32 in the above constitution, ifthe wheel 2 is distorted, torque can be transmitted from the inwheelmotor 3 to the wheel 2.

When an elastic material such as rubber is used in the above elasticmember 32, the material constituting the above elastic member 32preferably has a vertical elastic coefficient of 1 to 120 MPa. The abovevertical elastic coefficient is more preferably 1 to 40 MPa.

When the hub portion 4 is provided with a connection portion 4D for thedrive shaft 9 like an ordinary automobile as shown in FIG. 49, powerfrom a car power engine or motor other than the inwheel motor 3 can betransmitted to the wheel 2 through the drive shaft 9. Therefore, byconnecting the output shaft of a gasoline engine car to the hub portion4 of the inwheel motor system of this embodiment, a hybrid car can beconstructed.

Embodiment 12

FIG. 50 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 12. In FIG. 50, reference numeral 1 denotes atire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b,and 3 denotes an inwheel motor of an outer rotor type which comprises astator 3S fixed to a non-rotary case 3 a provided on the inner side inthe radial direction and a rotor 3R fixed to a rotary case 3 b rotatablyconnected to the above non-rotary case 3 a through a bearing 3 j andprovided on the outer side in the radial direction.

Reference numeral 4 represents a hub portion connected to the wheel 2 atits rotation axis, 5 represents a knuckle which is a part around thewheel of the vehicle and connected to upper and lower suspension arms 6a and 6 b, 7 represents a suspension member which is a shock absorber orthe like, and 8 represents a brake which is a brake disk mounted to theabove hub portion 4.

Reference numeral 33 denotes a motor buffer unit for connecting theabove inwheel motor 3 to a car body 100 side, 34 denotes a flexiblecoupling which is a driving force transmission unit having the sameconstitution as the above Embodiment 4 and interposed between theinwheel motor 3 and the wheel 2, and 35 denotes a direct-acting guideunit having the same constitution as the above Embodiment 4 andinterposed between the above non-rotary case 3 a and the knuckle 5. Thisdirect-acting guide unit 35 is provided with a spring member 36 forpreventing a collision between the wheel 2 and the inwheel motor 3,which is not directly connected to the above non-rotary case 3 a butonly to the knuckle 5.

The above motor buffer unit 33 comprises a motor arm 33 a extendingtoward the car body 100 and a damper 33 b which is an elastic member orspring member for connecting this motor arm 33 a to the car body 100.The above motor arm 33 a connected to the car body 100 side by thisdamper 33 b is used to support the non-rotary case 3 a of the inwheelmotor 3. Therefore, the inwheel motor 3 is vibrated not in the rotationdirection but only in the vertical direction with respect to the carbody 100 and wheel 2 by the flexible coupling 34 so that torque can betransmitted efficiently and the above motor 3 is mounted on the car body100 side by the above motor buffer unit 33. Thus, the inwheel motor 3can be mounted to a sprung portion.

Since the non-rotary case 3 a of the inwheel motor 3 is mounted on thecar body 100 side by the motor buffer unit 33 in the inwheel motorsystem of Embodiment 12, the inwheel motor 3 is mounted to a sprungportion, thereby making it possible to reduce the unsprung mass.Therefore, TCFF can be reduced and the running stability of the vehiclecan be improved.

In this embodiment, the spring member 36 for preventing a collisionbetween the wheel 2 and the inwheel motor 3 plays the role of a bumprubber for preventing a collision between the wheel 2 and the inwheelmotor 3. Therefore, even when the suspension makes a great stroke by therolling of the car body, it is possible to prevent a collision betweenthe wheel 2 and the inwheel motor 3. Even when the above spring member36 for preventing a collision is interposed between the rotary case 3 band the wheel 2, the same effect can be obtained. The above springmember 36 for preventing a collision may be interposed between the caseand the knuckle, or both between the wheel and the motor and between thecase and the knuckle.

As shown in FIG. 51, the non-rotary case 3 a of the inwheel motor 3 andthe knuckle 5 are interconnected by a buffer member 37 which is a springmember in addition to the above direct-acting guide unit 35 and by thespring member 36 for preventing a collision, thereby making it possibleto further reduce TCFF. That is, the inwheel motor 3 is connected to theknuckle 5 which is an unsprung mass corresponding portion of the vehicleby the buffer member 37, whereby the mass of the inwheel motor 3functions as the weight of a so-called dynamic damper for the unsprungmass. Therefore, TCFF can be further reduced when the vehicle runs overan uneven road, and the road holding properties of the vehicle can beimproved. Since the mass of the inwheel motor 3 can be separated fromthe unsprung mass corresponding portion of the vehicle by the aboveconstitution, even when the vehicle runs over a bad road, vibration isnot directly transmitted to the above inwheel motor 3, and a load on theinwheel motor 3 imposed by vibration is reduced.

EXAMPLE 2

The graph of FIG. 56 shows the analytical results of the level of TCFFin the inwheel motor system of Embodiment 12 and the prior art systemusing car vibration models as shown in FIGS. 52 to 54 and the table ofFIG. 55 when the vehicle runs over an uneven road. Comparative Example2-1 is an electric car which does not employ an ordinary inwheel motorsystem and in which the mass of the motor corresponds to the sprung massas the motor is mounted on the car body side.

In FIG. 56, the horizontal axis shows vibration frequency (Hz) and thevertical axis shows the level (N) of TCFF.

For example, as the motor is mounted to the wheel or knuckle in theconventional inwheel system shown in FIG. 79, the mass of the motorcorresponds to the unsprung mass. The car vibration model is atwo-freedom unsprung vibration model (Comparative Example 2-2) as shownin FIG. 52. Describing in more detail, the vibration model in which theunsprung mass m₁ is connected to the contact face of the tire by theelastic member k₁ and the dash pot c₁ and in which the above unsprungmass m₁ and the sprung mass m₂ are interconnected by the elastic memberk₂ and the dash pot c₂ becomes a model in which the mass of the inwheelmotor is added to the above unsprung mass m₁. Thus, as the unsprung massincreases when the motor is directly mounted, the level of TCFF risesand the capability of the tire deteriorates (FIG. 56).

To maintain this level of TCFF at the level of the above ComparativeExample 2-1, the total weight of the motor and a part around the wheelmust be made equal to that of the prior art system as shown inComparative Example 2-3. However, a serious cost rise is expectedbecause a large amount of a light alloy must be used to greatly reducethe weight of the part around the wheel while the requirement forstrength is satisfied, which cannot be said to be practical.

In contrast to this, in the inwheel motor system of the presentinvention, the inwheel motor is mounted on the car body 100 side by amotor buffer unit corresponding to the elastic member k₃ and the dashpot C₃ as shown in FIG. 50. Therefore, the car vibration model is athree-freedom model (Example 2-1) in which the mass m₃ of the motor isconnected to the sprung mass m₂ by the elastic member k₃ and the dashpot C₃ as shown in FIG. 53 in the two-freedom model shown in FIG. 52.

Therefore, as shown in the graph of FIG. 56, the level of TCFF can bemade equal to that of an electric motor which does not employ anordinary inwheel motor system shown in the above Comparative Example 1.

When the inwheel motor is mounted on the car body side by the abovebuffer unit, and the buffer member consisting of the elastic member k₄and the dash pot c₄ is added between the inwheel motor and the partaround the wheel as shown in FIG. 51, the car vibration model becomes amodel as shown in FIG. 54 in which the mass m₃ of the motor is connectedto the sprung mass m₂ by the elastic member k₃ and the dash pot C₃ andin which the mass m₃ of the above motor is connected to the unsprungmass m₁ to become the weight of a dynamic damper (Example 2-2).

Therefore, as shown in the graph of FIG. 56, the level of TCFF can bereduced by 10 Hz or more without increasing the weight of the vehicleexcessively.

A 10 Hz or more further reduction in the level of TCFF can be achievedby increasing spring force k₄ between the motor and the part around thewheel and by reducing spring force k₃ between the inwheel motor and thecar body like Example 2-3.

Embodiment 13

In the above Embodiments 1 to 12, an ordinary inwheel motor 3 has beendescribed. When a geared motor consisting of a hollow inner rotor typemotor and a speed reducing gear is mounted to an unsprung masscorresponding portion of the vehicle by a buffer member or a bufferunit, TCFF is reduced, thereby making it possible to improve roadholding properties and transmit torque to the wheel without fail.

FIG. 57 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 13, and FIG. 58 is a sectional view of the keysection of the system. In these figures, reference numeral 1 denotes atire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b, 40denotes a geared motor (inwheel motor) which incorporates an electricmotor 41 and a planetary speed reducer 42 in a motor case 43, 4 denotesa hub portion connected to the wheel 2 at its rotation axis, 5 denotes aknuckle which is a part around the wheel of the vehicle and connected toupper and lower suspension arms 6 a and 6 b, 7 denotes a suspensionmember which is a shock absorber or the like, and 8 denotes a brakewhich is a brake disk mounted to the above hub portion 4.

Reference numeral 44 represents an elastic member for connecting themotor case 43 which is the non-rotary portion of the geared motor 40 tothe knuckle 5, and 45 represents a shaft having a universal joint 45 j,for connecting the output shaft of the planetary speed reducer 42 to thewheel 2.

The electric motor 41 of the geared motor 40 is a hollow inner rotortype motor which comprises a stator 41S fixed to a non-rotary case 41 aprovided on the outer side in the radial direction and a rotor 41R fixedto a rotary case 41 b rotatably connected to the above non-rotary case41 through a bearing 41 j and provided on the inner side in the radialdirection. The above non-rotary case 41 a is mounted to the motor case43 connected to the knuckle 5 which is a fixed portion by the elasticmembers 44, and the rotary case 41 b is connected to the sun gear 42 aof the planetary speed reducer 42 by a connection member 41 d androtatably connected to an inner wall 43 a constituting the hollow shaftportion of the motor case 43 through a bearing 43 b. In the aboveplanetary speed reducer 42, the rotation speed of the above sun gear 42a is changed to a speed corresponding to the rotation speed of theplanetary gear 42 b to be reduced and transmitted to the wheel 2 by theabove shaft 45 connected to the output shaft of the planetary speedreducer 42 from a carrier 42 c.

To interconnect the motor case 43 and the knuckle 5 by the elasticmembers 44 in this embodiment, as shown in FIG. 59, four elastic members44 are arranged symmetrical on a disk-like motor attachment member 46,and a motor attachment unit 47 which has direct-acting guides 47 k,interposed between the above elastic members 44 and 44, for guiding themotor case 43 in the vertical direction is used to interconnect themotor case 43 and the knuckle 5, thereby limiting the moving directionof the motor to the vertical direction of the wheel.

Since the motor case 43 which is the non-rotary portion of the gearedmotor 40 is mounted to the knuckle 5 by the elastic members 44 asdescribed above to float mount the above geared motor 40 to an unsprungmass corresponding portion which is a part around the wheel of thevehicle, the axis of the motor and the axis of the wheel can moveseparately in the radial direction. Therefore, the mass of the motor isseparated from the unsprung mass corresponding portion of the vehicleand functions as the weight of a so-called dynamic damper like the aboveEmbodiments 1 to 12 to cancel unsprung vibration at the time of runningover an uneven road, thereby reducing TCFF. Therefore, the road holdingproperties of the vehicle can be improved and vibration applied to thegeared motor 40 at the time of running over a bad road can be reduced,thereby making it possible to reduce a load on the above motor 40imposed by vibration. Since the motor case 43 and the knuckle 5 areinterconnected by the elastic members 44 and the motor attachment unit47 having the direct-acting guides 47 k for guiding the motor case 43 inthe vertical direction, the geared motor 40 can move in the verticaldirection of the vehicle but not in the rotation direction by therestriction of the direct-acting guides 47 k. Therefore, the rotation ofthe motor case 43 which is a non-rotary portion can be prevented.Although the motor vibrates and the axis of the motor and the axis ofthe wheel become eccentric from each other at the time of running over abad road, the torque of the motor can be transmitted smoothly by usingthe above universal joint 45 j even when these axes become eccentricfrom each other.

Since the mass of the vehicle is supported by the hub portion 4 in theinwheel motor system of this embodiment, a load on the body of the motor40 is small. Therefore, a change in the air gap between the rotor 41Rand the stator 41S can be made small, whereby the stiffness of the casecan be reduced and the motor 40 can be made lightweight.

Since the geared motor 40 is connected to the hub portion 4 by the shaft45 having the universal joints 45 j passing through the center thereof,even when the geared motor 40 moves relative to a portion around thewheel, torque can be transmitted to the wheel 2 without fail.

Since the geared motor 40 is used as the inwheel motor in thisembodiment, compared with a case where a direct drive motor of an outerrotor type is used, the capacity of the motor can be made smaller togenerate the same torque and the mass of the motor can be reduced,thereby making it possible to reduce the total weight of the vehicle andthe production cost of the motor. Further, since the gear ratio of thegeared motor 40 can be selected, a torque curve can be freely set withthe same motor, thereby improving the general-applicability of the motorcompared with a direct drive motor of an outer rotor type.

EXAMPLE 3

The graph of FIG. 64 shows the analytical results of the level of TCFFin the inwheel motor system of the above Embodiment 13 and the system ofthe prior art using car vibration models at the time of running over anuneven road as shown in FIGS. 60 to 62 and the table of FIG. 63.

Comparative Example 3-1 is an electric car which does not employ anordinary inwheel motor system in which the mass of the motor correspondsto the sprung mass as the motor is mounted on the car body side.

Since the motor is mounted to an unsprung mass corresponding portionsuch as the wheel or knuckle in the conventional inwheel motor system, acar vibration model is a two-freedom unsprung vibration model as shownin FIG. 60 (Comparative Example 3-2 in the table of FIG. 63). Describingin more detail, the model is a vibration model in which the mass of theinwheel motor is added to the above unsprung mass m₁ in the vibrationmodel in which the unsprung mass m₁ is connected to the contact face ofthe tire by the elastic member k₁ and the dash pot c₁, and the aboveunsprung mass m₁ and the sprung mass m₂ are interconnected by theelastic member k₂ and the dash pot c₂. Thus, when the motor is directlymounted to an unsprung mass corresponding portion, the unsprung massincreases with the result that the level of TCFF rises and the roadholding properties deteriorate as shown in FIG. 64.

To maintain this level of TCFF at the level of the above ComparativeExample 3-1, the total weight of the motor and a part around the wheelmust be made equal to that of the prior art system. However, to greatlyreduce the weight of the part around the wheel while the requirement forstrength is satisfied, a serious cost rise is expected due to use of alarge amount of a light alloy, which cannot be said to be practical.

Meanwhile, as means of reducing TCFF at the time of running over anuneven road without reducing the above weight, there is a method called“dynamic damper” represented by a model shown in FIG. 61 (ComparativeExample 3-3 in the table of FIG. 63). This is a three-freedom model inwhich new weight m₃ is added to the unsprung mass m₁ of the two-freedommodel of FIG. 60 by the elastic member k₃ and the dash pot C₃ and hasthe effect of reducing TCFF as shown in FIG. 64.

This method is more effective as the additional weight m₃ increases. Asthis additional weight merely serves to increase the weight of thevehicle besides to reduce the above change, it has a bad influence onthe vehicle. Therefore, there is limitation to the increase of the aboveweight m₃.

In contrast to this, since the inwheel motor (geared motor) 40 ismounted on the car body side by the elastic members 44 in the inwheelmotor system of the present invention as shown in FIG. 57, the carvibration model can be represented by a three-freedom model (Example3-1) in which the mass of the motor is connected to the unsprung mass m₁by the elastic member k₃ and the dash pot c₃ as shown in FIG. 62. Thisis a model in which the mass of the motor added to the unsprung mass m₁is removed and this mass of the motor is designated as additional weightm₃ used in the dynamic damper in FIG. 61. Therefore, as shown in thegraph of FIG. 64, the level of TCFF can be made equal to that of anelectric car which does not employ an ordinary inwheel motor systemshown in the above Comparative Example 3-1 without increasing the weightof the vehicle excessively.

When the weight of the motor and the weight of the part around the wheelare both reduced in the above Example 3-1 (Example 3-2), when theelastic coefficient of the elastic member is reduced (Example 3-3) andwhen both of them are combined (Example 3-4), the level of TCFF can befurther reduced.

Embodiment 14

FIG. 65 is a diagram showing the constitution of an inwheel motor systemaccording to Embodiment 14. In the figure, reference numeral 1 denotes atire, 2 denotes a wheel consisting of a rim 2 a and a wheel disk 2 b,and 3 denotes an inwheel motor of an outer rotor type which comprises astator 3S fixed to a non-rotary case 3 a provided on the inner side inthe radial direction and a rotor 3R fixed to a rotary case 3 b rotatablyconnected to the above non-rotary case 3 a through a bearing 3 j andprovided on the outer side in the radial direction.

Reference numeral 4 represents a hub portion connected to the wheel 2 atits rotation axis, 5 represents a knuckle which is a part around thewheel of the vehicle and connected to upper and lower suspension arms 6a and 6 b, 7 represents a suspension member which is a shock absorber orthe like, and 8 represents a brake which is a brake disk mounted to theabove hub portion 4.

In this embodiment, the rotary case 3 b of the above inwheel motor 3 isconnected to the wheel 2 by a flexible coupling 51. The above flexiblecoupling 51 is identical to the flexible coupling 18, 19 or 20 shown inFIGS. 22 to 25 of Embodiment 4, FIGS. 29 and 30 of Embodiment 5 or FIGS.32 and 33 of the above Embodiment 6.

Meanwhile, the non-rotary case 3 a is mounted to the peripheral portionof a disk-like motor attachment member 52 having a cut-out portion 52Sin the center as shown in FIG. 66. This motor attachment member 52 isconnected to a hollow oval disk-like motor vertical support member 55having a long axis in the longitudinal direction by dampers 53 which arespring members mounted to slide guides 53G for guiding in the verticaldirection of the vehicle and direct-acting guides 54 for guiding in thevertical direction of the vehicle. Further, this motor vertical supportmember 55 is mounted to the knuckle 5 which is a fixed portion byelastic members 56, direct-acting guides 57 for guiding in thelongitudinal direction of the vehicle and a hollow disk-like knuckleattachment member 58. In this embodiment, four dampers 53 and fourdirect-acting guides 54 for interconnecting the above motor attachmentmember 52 and the motor vertical support member 55, and four elasticmembers 56 and four direct-acting guide 57 for interconnecting the abovemotor vertical support member 55 and the knuckle attachment member 58are disposed alternately and symmetrically in the circumferentialdirection.

Thereby the inwheel motor 3 can be supported by the direct-acting guidesand the elastic members in the vertical direction of the vehicle, andthe vertical direction support part and the knuckle which is a partaround the wheel can be supported by the direct-acting guides and theelastic members in the longitudinal direction of the vehicle.

That is, since the non-rotary case 3 a of the inwheel motor 3 isconnected to the hollow oval disk-like motor vertical support member 55by the dampers 53 and the direct-acting guides 54 for guiding in thevertical direction of the vehicle, the inwheel motor 3 can be floatmounted to an unsprung mass corresponding portion which is a part aroundthe wheel of the vehicle, and the axis of the motor and the axis of thewheel can move separately only in the vertical direction. Therefore, themass of the motor is separated from the unsprung mass of the vehicle andfunctions as the weight of a so-called dynamic damper. As the weight ofthe dynamic damper cancels unsprung vibration at the time of runningover an uneven road, TCFF is reduced, the road holding properties of thevehicle are improved, and a load on the motor 3 imposed by vibration atthe time of running over a bad road can be made small.

Since the motor 3, the motor attachment member 52 and the motor verticalsupport member 55 are connected to the knuckle 5 by the elastic members56 and the direct-acting guides 57 for guiding in the longitudinaldirection of the vehicle to support the knuckle in the longitudinaldirection of the vehicle, the axis of the motor and the axis of thewheel can move separately in the longitudinal direction of the vehicleas well, whereby the tire longitudinal force fluctuation can be reducedand the performance of the tire can be stabilized.

Since the rotary case 3 b of the motor 3 and the wheel 2 areinterconnected by the flexile coupling 51 in this embodiment, rotatingtorque from the rotor 3R can be efficiently transmitted to the wheel 2and torque can be smoothly transmitted even when the axis of the motorand the axis of the wheel become eccentric from each other due to thevibration of the motor at the time of running over a bad road.

A constant-velocity universal joint as shown in FIGS. 14 and 15 of theabove Embodiment 2 may be used as means of interconnecting the aboverotary case 3 b and the wheel 2. Since the inwheel motor 3 moves withinthe wheel 2 in the vertical and longitudinal directions when therotation center of the wheel-side joint is shifted from the rotationcenter of the motor-side joint, torque can be smoothly transmitted evenwhen they become eccentric from each other.

Since the mass of the vehicle is supported by the hub portion 4 in thisembodiment, a load on the body of the motor 3 is small. Therefore, achange in the air gap between the stator and the rotor can be reduced,thereby making it possible to reduce the stiffness of the case and theweight of the motor 3.

In the above embodiment, an outer rotor type motor is used as theinwheel motor 3. Even when an inner rotor type motor 3I is used as shownin FIG. 67, the same effect can be obtained.

Embodiment 15

In the above Embodiment 14, the inwheel motor 3 which is a direct drivemotor is mounted. Similarly, as shown in FIG. 68 and FIG. 69, a gearedmotor 40 which comprises an electric motor 41 and a speed reducing gear(planetary speed reducer) 42 in a motor case 43 shown in FIGS. 57 and 58of the above Embodiment 13 may be mounted.

To mount the geared motor 40, as shown in FIG. 70, the non-rotary motorcase 43 is mounted to a hollow disk-like motor attachment member 63 bydirect-acting guides 61 for guiding in the vertical direction of thevehicle and elastic members 62, and this motor attachment member 63 ismounted to the knuckle 5 which is a fixed portion by a hollow disk-likeknuckle attachment member 66 by elastic members 64 and direct-actingguides 65 for guiding in the longitudinal direction of the vehicle. Likethe above Embodiment 13, the output shaft of the speed reducing gear 42and wheel 2 are interconnected by a shaft 45 having a universal joint 45j (see FIG. 68 and FIG. 69).

The rotation speed of the rotor 41R is changed to a speed correspondingto the rotation speed of the planetary gear 42 b which turns around asun gear 42 a to be reduced and transmitted to the wheel 2 by the aboveshaft 45 connected to the output shaft of the planetary speed reducer 42from a carrier 42 c.

In this embodiment, four direct-acting guides 61 and four elasticmembers 62 are arranged alternately and symmetrically in thecircumferential direction to connect the above motor case 43 to themotor attachment member 63, and four elastic members 64 and fourdirect-acting guides 65 are arranged alternately and symmetrically inthe circumferential direction to connect the above motor attachmentmember 63 to the knuckle attachment member 66.

Thereby, the geared motor 40 is supported by the direct-acting guidesand the elastic members in the vertical direction of the vehicle, andthe vertical direction support member and the knuckle which is a partaround the wheel are supported by the direct-acting guides and theelastic members in the longitudinal direction of the vehicle. Therefore,the above geared motor 30 can be float mounted to an unsprung masscorresponding portion which is a part around the wheel of the vehicle,and the axis of the motor and the axis of the wheel can move separatelyin the radial direction and also in the longitudinal direction of thevehicle. As a result, TCFF can be reduced, the road holding propertiesof the vehicle can be improved, the tire longitudinal force fluctuationcan be reduced, and accordingly, the performance of the tire can bestabilized.

Since the geared motor 40 is connected to the hub portion 4 by the shaft45 having a universal joint 45 j passing through the center thereof,even if the geared motor 40 moves relative to the part around the wheel,torque can be transmitted to the wheel 2 without fail.

EXAMPLE 4

The graphs of FIG. 76 and FIG. 77 show the analytical results offluctuations in tire contact force and longitudinal force in the inwheelmotor system of the above Embodiment 15 and the system of the prior artusing car vibration models at the time of running over an uneven road asshown in FIGS. 71 to 74 and the table of FIG. 75. FIGS. 71( a) to 74(b)show vertical direction vibration models and FIGS. 71( b) to 74(b) showlongitudinal direction vibration models. In FIGS. 76 and 77, thehorizontal axis shows vibration frequency (Hz) and the vertical axisshows the level of TCFF (N) and the level of tire longitudinal forcefluctuation (N).

Comparative Examples 4-1 to 4-3 are ordinary suspension type electricvehicles (EV) in which the mass of the motor corresponds to the sprungmass as the motor is mounted on the car body side. Therefore, the carvibration models of the above examples are two-freedom unsprungvibration models shown in FIGS. 71( a) and 71(b). Describing in moredetail, the vibration models are a model in which the mass of theelectric motor is added to the unsprung mass m₁ in the vibration modelin which the unsprung mass m₁ is connected to the contact face of thetire by the elastic member k₁ and the dash pot c₁, and the aboveunsprung mass m₁ and the sprung mass m₂ are interconnected by theelastic member k₂ and the dash pot c₂.

Since the motor is mounted to the wheel or the knuckle in a vehicle(IWM) which employs the inwheel motor system of the prior art shown inFIGS. 78 to 80, the mass of the motor corresponds to the unsprung mass.Therefore, the car vibration model is a two-freedom unsprung vibrationmodel in which the mass of the inwheel motor is added to the unsprungmass m₁ as shown in FIGS. 72( a) and 72(b) (Comparative Example 4-4).When the motor is directly mounted to an unsprung mass correspondingportion like Comparative Example 4-4, the unsprung mass increases withthe result that the level of TCFF rises and the road holding propertiesdeteriorate as shown in FIG. 76. Also, as shown in FIG. 77, the level oftire longitudinal force fluctuation increases and the performance of thetire become unstable.

Then, when the unsprung mass is reduced in Comparative Example 4-1 likethe above Comparative Example 4-2, or the stiffness in the longitudinaldirection of the suspension is increased like the above ComparativeExample 4-3, the level of tire longitudinal force fluctuation isreduced. Since the mass of the inwheel motor is added to the unsprungmass m₁ in this Comparative Example 4-4, the level of tire longitudinalforce fluctuation rises.

Therefore, to maintain this level at the level of the above ComparativeExample 4-1 in which the motor is not mounted, the total weight of themotor and a part around the wheel must be made equal to that of theprior art system. However, in order to greatly reduce the weight of thepart around the wheel while the requirement for strength is satisfied, aserious cost rise is expected due to use of a large amount of a lightalloy, which cannot be said to be practical.

Meanwhile, as means of reducing TCFF at the time of running over anuneven road without reducing the above weight, there is a method called“dynamic damper” represented by models shown in FIGS. 73( a) and 73(b)(Comparative Example 4-5 in the table of FIG. 75). These are athree-freedom model in which new weight m₃ is added to the unsprung massm₁ of the two-freedom models shown in FIGS. 72( a) and 72(b) by theelastic member k₃ and the dash pot C₃ and has the effect of reducing thelevel of TCFF and the level of tire longitudinal force fluctuation.

This method is more effective as the additional weight m₃ increases. Asthis additional weight merely serves to increase the weight of thevehicle besides to reduce the above change levels, it has a badinfluence on the vehicle. Therefore, there is limitation to the increaseof the above weight m₃.

In contrast to this, since the inwheel motor 3 (3I, 40) is mounted onthe car body side by the elastic members and/or attenuation unit asshown in FIG. 65, FIG. 67 or FIG. 68 in the inwheel motor system of thepresent invention, the car vibration model is a three-freedom model(Example 4-1 of FIG. 75) in which the mass of the motor is connected tothe unsprung mass m₁ by the elastic member k₃ and the dash pot C₃ asshown in FIGS. 74( a) and 74(b). This model is obtained by removing themass of the motor added to the unsprung mass m₁ and using this mass ofthe motor as additional weight m₃ for use in the dynamic damper in FIGS.74( a) and 74(b). Therefore, as shown in the graphs of FIG. 76 and FIG.77, the level of TCFF and the level of tire longitudinal forcefluctuation can be made equal to those of an electric car which does notemploy an ordinary inwheel motor system shown in the above ComparativeExample 1 without increasing the weight of the vehicle excessively.

Since the weight of the dynamic damper increases when the motor is madeheavy in the above Example 1 (Example 4-2 of FIG. 75), the level of TCFFand the level of tire longitudinal force fluctuation can be furtherreduced.

As the above change levels rise when the elastic coefficient of theelastic member is increased (Example 4-3), the elastic coefficient ofthe elastic member is preferably made small.

INDUSTRIAL FEASIBILITY

As described above, according to the present invention, when the inwheelmotor is to be mounted to the direct drive wheel, the above motor ismounted to an unsprung mass corresponding portion of the vehicle by abuffer member or buffer unit to function as the weight of a dynamicdamper for the unsprung mass. Therefore, the level of TCFF at the timeof running over an uneven road can be reduced, the road holdingproperties of the vehicle can be improved, and further a load on theinwheel motor imposed by vibration can be reduced.

By employing the inwheel motor system of the present invention, aninwheel motor vehicle having excellent space efficiency and transmissionefficiency of driving force and high road holding properties can berealized.

1. A method of mounting an inwheel motor for driving a wheel, to anunsprung portion of a vehicle suspending the vehicle body through asuspension member for suspending a vehicle body, said method comprising:mounting said motor to said unsprung portion via a damping memberdedicated only to said motor such that a mass of said motor serves as amass in a dynamic damper.
 2. The method of mounting an inwheel motoraccording to claim 1, wherein a non-rotary ease of the motor and aknuckle are interconnected by a first elastic member, and a rotary caseof the motor and the wheel are interconnected by a second elasticmember.
 3. A method of mounting an inwheel motor for driving a wheel, toan unsprung portion of a vehicle suspending the vehicle body through asuspension member for suspending a vehicle body, said method comprising:mounting said motor to a vehicle body side via a damping memberdedicated to said motor such that a mass of said motor serves as a massin a dynamic damper.
 4. An inwheel motor system for driving a wheelusing a electric motor, said system comprising: a vehicle body, anunsprung portion of the vehicle suspending the vehicle body through asuspension member for suspending the vehicle body, said motor beingmounted to the unsprung portion of a vehicle suspending the vehicle bodythrough a suspension member for suspending a vehicle body, wherein saidmotor is mounted to at least one of said unsprung portion and thevehicle body side via a damping member that is dedicated to said motorsuch that a mass of said motor serves as the mass in a dynamic damper.5. The inwheel motor system according to claim 4, wherein a buffermember is provided between the non-rotary case of the motor and aknuckle or/and between the rotary case and the wheel.
 6. The inwheelmotor system according to claim 4, wherein a non-rotary case of themotor for supporting the stator of the motor and a knuckle which is apart around the wheel of a vehicle are interconnected by a first elasticmember, and a rotary case of the motor for supporting a rotor and thewheel are interconnected by a second elastic member.
 7. The inwheelmotor system according to claim 6, wherein at least one or both of thefirst and second elastic members are an air spring.
 8. The inwheel motorsystem according to claim 6, wherein the second elastic member iscylindrical, one end of this cylinder is connected to the wheel, and theother end is connected to the rotary case.
 9. The inwheel motor systemaccording to claim 6, wherein the wheel and the rotary case areinterconnected by 16 or less other elastic members disposed at equalintervals in parallel to a direction tangent to a circumference of thewheel.
 10. The inwheel motor system according to claim 9, wherein rotaryjoint units whose axes are in the tangent direction of the motor areprovided on both end faces in the width direction of the other elasticmembers.
 11. The inwheel motor system according to claim 6, wherein ribsextending from the rotary case toward the wheel and ribs extending fromthe wheel toward the rotary case are interconnected by an elastic memberat a plurality of sites.
 12. The inwheel motor system according to claim6, wherein the vertical elastic coefficient of a material constitutingthe first and second elastic members is 1 to 120 MPa.
 13. The inwheelmotor system according to claim 6, wherein the vertical elasticcoefficient of a material constituting the first and second elasticmembers is 10 to 300 GPa.
 14. The inwheel motor system according toclaim 6, wherein the first elastic member has a lower elastic modulus ina vertical direction of the vehicle than an elastic modulus in alengthwise direction of the vehicle.